If you would like to partake in governance, you would need to first stake a portion of your YFI into the yGov V2 pool on https://ygov.finance and then register to vote.
Your currently staked tokens will enable you to vote on the active proposals.
Do take note of the vote lock of 3-days on your currently staked YFI applies, until the expiry of your last voted proposal; whether approved or rejected. (Duration of proposal voting lasts 3-days)
The governance token YFI is traded on many of the available exchanges, and on DEXs too.