On your profile page, languages are listed in the bottom right (at the bottom of the column under the green "Profile Settings" button).
If you mouse over it, you'll see a small plus sign to the right--click on that to add language proficiency.
On my profile page under Languages, it says: English: Fluent
It's been that way since I signed up in 2011 when it was oDesk.
Do you have any other suggestions? I appreciate the help.
If you click the edit icon (pencil) next to that entry on your profile, you'll see radio buttons to indicate your level of proficiency. Fluent is not the highest level--switch that to native.