For those curious, the process is described here [1]. As a voter, you go to a table and pick a ballot that represents your choice. You can pick a pre-printed ballot with your party's name on it, or you can take a blank ballot and write it manually. If you want to keep your choice secret, you can pick a bunch of random ballots, but submit just one of them.
For comparison, in Sweden's neighbouring country of Norway, the voting booth where you pick and fill out the ballot is covered with a curtain. You fill out the ballot (they're all printed on the same type of paper), which you fill out and fold so that it hides the contents. You then go over to an election worker, who confirms your identity and gives you an envelope to put the ballot in, which you then seal and put in the drop box.
For comparison, in Sweden's neighbouring country of Norway, the voting booth where you pick and fill out the ballot is covered with a curtain. You fill out the ballot (they're all printed on the same type of paper), which you fill out and fold so that it hides the contents. You then go over to an election worker, who confirms your identity and gives you an envelope to put the ballot in, which you then seal and put in the drop box.
[1] https://en.wikipedia.org/wiki/Elections_in_Sweden#Voting