The three overlapping ellipses form seven curved regions - place one tile in each region so that the tiles in any one ellipse can be re-arranged into an eight-letter solution to the corresponding clue!
The first word I got (perhaps surprisingly) was
fighter = PUGILIST.
Realising that "NG" is probably at the end of a word and preceded by a vowel, it didn't take much fiddling to get
pound = STERLING.
And then, by a process of elimination, the final word must be
prize = PULITZER.
Oh and the title?
"Beatboxer" means a boxer who beats people, not the other meaning.