In practice, it's a little convoluted ( https://www.bloomberg.com/view/articles/2016-05-13/t-rowe-pr... , that story is about takeover bids, but I'm sure the process is similar).

Occasionally, I get postcards asking me to nominate a proxy for some upcoming shareholders meeting due to investments I own through my 401(k). I guess that you should be on the lookout for that kind of postcard and follow the instructions.

Do nothing. The board doesn't back it, and they get your vote if you don't bother.

If you use a brokerage like Ameritrade or Robinhood usually they'll just email you your proxy so you can vote on it.