Additional comment to the excellent answer from Virginia:
- you need to check your test results vs those listed here on WikiTree. It's only an indication that a potential relative through a common ancestor has also tested at the DNA testing companies mentioned and by no means it certain that you're automatically related (unless you have a very close relationship). But it allows you to get in touch with these people and use 3rd party tools to perform triangulation (either manually or automatically) to determine if you and two other independent matches here on WikiTree have most likely inherited ancestral DNA from that common ancestor.
- please do not forgot that DNA is very random, as I mentioned in the previous point having a common ancestor "on paper" doesn't mean automatically you're related.
As you have tested at 23andMe I'd recommend that you also check out Your DNA family
It will help you get a lot more out of your 23andMe DNA test (eg. automatic triangulation, automatic identification of MRCA's, saves your matching segments even when 23andMe removes them from your matches when you're over their 2000 matching segments limit).
As WT'er like to work together with other people on their ancestry you will be pleased to read that it offers private discussion forums for each triangulated group that is build (usually people have up 250 TG's unless they have endogamy amongst their ancestors).
This video 12 steps to identify your common ancestor highlights the methodology behind the app and showcases the actual app with real data.
Disclaimer: I'm the author of "Your DNA family"
PS: an integration with WikiTree to retrieve your ancestors/related descendants from the WT family tree is on the near roadmap