Either (A) input the mods in question into MoreClothing, which will allow you to make character codes involving them (requires installing MoreClothing which can be daunting to a new user) or (B) put a copy of each of the mods into the character folder the girl is going to be in (follow standard procedure for making a new girl - give them the appropriate folder in Mods.txt, add this folder to CharacterFolders, put in the Code.txt/Thumb.png) AND put a file in there called Mods.txt in which you list the filenames of all mods that will be loaded.
Let's say you wanted to use just Faceless' mermaid tail mod, which is titled mermaid.mod. You'd put that in the folder of the girl you're making and in the Mods.txt file, you'd have "mermaid.mod" as one line. Then, the girl SHOULD load in with the mermaid tail when you initialize her. Expand the Mods.txt file as far as is necessary (it sounds like you have 2 swf mods so yours would be 2 lines - if you have more and didn't bring up the others, it's 1 line per mod).
I'd suggest taking a quick look over this thread
[W.I.P] SDT Tutorial for Very Newbie User as well, as you would probably find some useful information there beyond what I've said (and that also should clear up any confusion my statements have brought up).