First of all, welcome to the forum and congratulations on your new horses!
You just need to make the decision and do it. Don't think, just do it. Have someone walk beside you and start off at an easy walk. Just block out the fear and focus on the horse. Once you face your fear head-on and overcome it, you'll be just fine.
I used to be afraid to ride my horse, but one day I just told myself I wasn't going to be afraid anymore. It worked. I just got on and took control. You can't give yourself time to second guess yourself. Just do it. Good luck!