Once you have the profile open for an interpreter, you can choose Languages from the menu

You will then see a screen with cards on it for the languages approved for that interpreter.  To add a new one, click the plus sign and fill in the fields.  Note that the rating is optional and is not currently used anywhere in Atrium.  In the upper right corner of each card are icons you can click to edit, disable and delete.  Note that if an interpreter has a language listed that they have not every had an assignment to use, you may delete.  If they have an assignment, you will not be permitted to delete it.  Should you want to make sure that the interpreter is never assigned in that language again in the future, click the No Entry icon to mark it as disabled.