enlarge (up)on (something)
To add or supply more information or details about something. I can see you aren't familiar with this material yet, so allow me to briefly enlarge upon it for you. I asked the boss to enlarge on the details of the proposal for me.
expand (up)on something
and enlarge (up)on somethingFig. to add detail to a report about something; to say more about something. Would you please expand upon that last remark? Would you care to enlarge upon your remarks?