It’s up to you to decide if a pen name is right for you. But first consider the following by Sylvia Day:
and Tracy Cooper-Posey.
That done now you have to pick a name. It should be memorable etc. but not ridiculous. Ask your editor for help if you’re not sure.
Now that you picked, do an extensive search on google etc. Why? Because you want to find out if 1) Someone already uses that name 2) What is going to pop up on google when someone searches for you and 3) Whether or not you will even be able to get a domain name even close to your name or site you want.
If your searches yield no one with that name or more likely, a tolerable number of people or sites pop up on that search, you are ready for the next step.