Yeah, so the Gallup poll really should have another question asking about support for proportional representation vs. first-past-the-post.
And then yes, in traditional proportional systems you vote for a list of candidates rather than a single candidate, the lists are the ones getting the seats based on vote totals. The seats can be distributed based on a fixed or flexible lists model
If you have a state that now has 10 reps each party would make a list of 10 people, then if party A gets 40%, party B 35%, C 15% and D 10% you'd get 4 people from the list proposed by A, 3 (or 4) from the list for B, 2 (or 1) from C and 1 from D