I cannot fill out or save the profile.

The second menu item on the left of the Control Panel, Update Profile, allows you to fill in your profile. Once filled with valid values at least all the required fields, pressing the button “Save profile”, if the page does not show errors marked in red, it turns into “Processing…” and shortly after a small green box appears in the upper right corner of the screen with the words “Saved successfully”. At that point the data entered has just been saved.
In the case of a Candidate type profile, the required fields include the entry of at least one work experience. A student who lacks this can repeat the school experience here.