Do you own these in a brokerage account? If so, you would sell them the way you would sell any other share.

Depending on the broker the step by step instructions may look different. But all basically involve clicking the holding and clicking sell at some point.

Or are you talking about company shares that you own from a job you’ve had? That’s likely to be different and you may need to look at the paperwork you have relating to those and contact the ‘share registry’ which should be listed on that paperwork.

Hope that’s useful, it’s hard to answer such a broad question.