I wish to combine 8 esp's into one, how do I go about doing this?
I tried selecting all the esp's and then saving, but the content doesn't appear in the newly saved esp file.

I'd advise against using TESVSnip as the likelihood of multiple forms with the same FormIDs in the resulting plugin is too great unless you ensure the last six characters in each and every form are unique pre-merge. For fun, link all 8 (just the plugins) and I'll see what I can do with FO3Edit? No promises and it might need to be an ESM/p pair to retain groups not recognized by FO3Edit.

That won't be necessary, I could do that myself. I wanted to know if it was possible with the Creation Kit.

AFAIK, there is no way to merge esp files using just the Creation Kit, unfortunately.

Found TEVSnip and will be using it to combine my esp's.