Path: Profile >> Settings >> Profile Information >> Language
Registered members of IdeaScale can set the system prompts to the language of their choice. By default, the Language option is set to the same language as the Workspace language. 
In the below image, the member has set the profile language to Spanish.
So when the member has logged in and is on the workspace landing page the main tabs or headings will be prompted in the language which is set by the member as his/her profile language.
In the below screenshot the member has the profile language set as Spanish and these are the tabs, titles and texts which will reflect in Spanish: Submit Idea field, Search Ideas, Active Campaigns, Archived Campaigns, Save button, Idea Submission form, Stage CTA block, In-app notification, Kudos counter, Leaderboard, Submit via email address on homepage.
On idea details page, the following will be displayed in Spanish (member profile language): Header tabs, Subscribe button, Previous/next idea indicator, Campaign stats, Annotation details, Linked ideas, Comments/activity/attachment tabs, Stages, Activity details.
This will not affect the foreign language in which the ideas are submitted or the language in which existing ideas are displayed unless Translation is enabled. In that case, Show original link will appear showing the idea in its original language.
The admins of the workspace and community will be able to see the settings and other backend pages in their profile language as well.