There are many guides to how to vote for witnesses, including one I wrote in November: https://steemit.com/witness/@mikepm74/make-your-voice-heard-use-your-witness-votes

Here's the short version:

You can go to https://steemit.com/~witnesses and input your votes (up to 30) in one by one. The current top 50 are listed, but you can vote for anyone with your witness votes. If there is someone you know is running a witness server who is not in the top 50, just type their name in the space provided under the Top 50, and your vote will be tallied. You can help push some smaller witnesses into the top 50.