We have users that author in different languages, how do we set it up to another source language.?

Several things must be set up in the CMS to allow authors to write in another language.
     The examples in this topic are for German, but the same principles can be applied to any locale.
1.     The LCA client tools' UIs can be set to German so the UI labels appear in German. To make this change, go to Publication Manager > Tools > Options > Display Language > Deutsch Tools>Options>SDL Tridions Docs/Knowledge Center\Accounts>Settings.
     the DAG is written in English and is not translated. Therefore, it is preferable for the writers to keep their client tools UIs in English even if the content they are writing is in another language, so they can more easily follow the instructions in the DAG.
2.     The user's Publication Manager language must be set to German. To make this change, go to Publication Manager > Tools > Options > Accounts > Settings then change to DE.
3.     The Editor Templates must be created in German. To do this, go to the Web UI > Repository > ProductDocumentation > System > Editor template then push to translation (into German) all of the latest versions of the existing objects, following the instructions in Push Objects into Translation[Link text cannot be resolved].
     the templates do not actually need to be translated (although they can be). A copy just needs to be created so there is a template to work from for German users.
4.     The user's language preference must be set to German so the objects created are based off of the German editor templates. To make this change, go to the Web UI > Settings > Users > User Preferences > [select user] > User Properties then change Language to DE.
An author can only write in one language at a time. To work on an English publication, close all publications, change all settings to EN-US, then open the English publication and start working. To switch to German, close all tools, change settings to German, then open the German publication.

Translating Content Written in German
The language settings must be changed to allow translation from German as the source language.
     the output uses the same files already created for English-source publications; no new output work is needed.
This change is made using the Web UI.
1.     Go to Settings > XML Translation Settings.
2.     Copy and paste the entire contents into a text editor as a backup.
3.     Copy all the rows that include the From and To languages. For example:
        <FromLanguage ref="EN-US">
            <ToLanguage ref="ES-ES"/>
            <ToLanguage ref="ES-MX"/>
            <ToLanguage ref="ES"/>
            <ToLanguage ref="ES-XM"/>
            <ToLanguage ref="EN-GB"/>
            <ToLanguage ref="FR"/>
            <ToLanguage ref="FR-CA"/>
            <ToLanguage ref="DE"/>
            <ToLanguage ref="IT"/>
            <ToLanguage ref="JA"/>
            <ToLanguage ref="KO"/>
            <ToLanguage ref="PT-BR"/>
            <ToLanguage ref="TR"/>
            <ToLanguage ref="ZH-CN"/>
            <ToLanguage ref="ZH-TW"/>
            <ToLanguage ref="RU"/>
        </FromLanguage>
4.     Paste them into the Web UI page below the section that lists the FromLanguage as EN-US.
5.     Edit the new list so that German becomes the "From" Language, and adding English as the "To" Language. For example:
<FromLanguage ref="EN-US">
            <ToLanguage ref="ES-ES"/>
            <ToLanguage ref="ES-MX"/>
            <ToLanguage ref="ES"/>
            <ToLanguage ref="ES-XM"/>
            <ToLanguage ref="EN-GB"/>
            <ToLanguage ref="FR"/>
            <ToLanguage ref="FR-CA"/>
            <ToLanguage ref="DE"/>
            <ToLanguage ref="IT"/>
            <ToLanguage ref="JA"/>
            <ToLanguage ref="KO"/>
            <ToLanguage ref="PT-BR"/>
            <ToLanguage ref="TR"/>
            <ToLanguage ref="ZH-CN"/>
            <ToLanguage ref="ZH-TW"/>
            <ToLanguage ref="RU"/>
        </FromLanguage>
<FromLanguage ref="DE">
            <ToLanguage ref="ES-ES"/>
            <ToLanguage ref="ES-MX"/>
            <ToLanguage ref="ES"/>
            <ToLanguage ref="ES-XM"/>
            <ToLanguage ref="EN-GB"/>
            <ToLanguage ref="FR"/>
            <ToLanguage ref="FR-CA"/>
            <ToLanguage ref="EN-US"/>
            <ToLanguage ref="IT"/>
            <ToLanguage ref="JA"/>
            <ToLanguage ref="KO"/>
            <ToLanguage ref="PT-BR"/>
            <ToLanguage ref="TR"/>
            <ToLanguage ref="ZH-CN"/>
            <ToLanguage ref="ZH-TW"/>
            <ToLanguage ref="RU"/>
        </FromLanguage>
The choice becomes English or German as your source language.