There’s more than one way to do it. You can simply have open party list proportional representation, where people vote for who gets on each party list and in what order. Then in the general election everyone picks parties and the seats are awarded proportionally according to the lists that were chosen by the voters.
Or, you can have a open election with any number of candidates running for office from any number of parties. Voters pick candidates using a method that lets them choose as many as they like, like Sequential Proportional Approval Voting. Then the seats are awarded to the winners, with the awarding method being the thing that creates proportional representation.
With the first way it’s extra important that candidates appeal to the party’s base. With the second way there’s potentially multiple strategies for winning a seat.
There’s more than one way to do it. You can simply have open party list proportional representation, where people vote for who gets on each party list and in what order. Then in the general election everyone picks parties and the seats are awarded proportionally according to the lists that were chosen by the voters.
Or, you can have a open election with any number of candidates running for office from any number of parties. Voters pick candidates using a method that lets them choose as many as they like, like Sequential Proportional Approval Voting. Then the seats are awarded to the winners, with the awarding method being the thing that creates proportional representation.
With the first way it’s extra important that candidates appeal to the party’s base. With the second way there’s potentially multiple strategies for winning a seat.