Once CRV holders vote-lock their veCRV, they can start voting on various proposals.
Anybody can create proposals but users need to follow the structure of a proposal which can be found by creating a new topic on the governance forum: https://gov.curve.fi/
Users who create proposals also need to create a corresponding CIP proposal at http://signal.curve.fi/
Using the signalling tool is completely free (no transaction fees) and you only need 1veCRV to create a proposal there.
Assuming you have at least 2,500 veCRV, you can also create an official DAO vote as long as it also comes with its topic presenting it on the governance forum.
Currently there are two type of votes: