iMac addon issues. *warning noob questions* lol

[JAG2_1977]

hi all. Love nui+!!!! i'm having problems getting any add-ons, such as QH or Carbonite, Recount, Omen, DBM, etc., to work. nui+ works fine but add-ons don't even show and if they do they crash the whole ui. i know im doing something wrong but don't know what. so here is what i do and if i can be directed to a site or answered here i would be very grateful.

(this is on an imac just as a reminder, if it makes a difference)

1. download nui+ and put it in 'Interface' folder
2. log in to WoW to ensure successful(.......always is)
3. go back to WoWI downloads and download all add-ons I need
4. open 'Interface' folder and then open 'Addons' folder.....put first add-on, recount, into 'Addons'
3. log into WoW to find out its not working

am i putting nui+ in wrong spot? should it be in the 'Addons' folder instead? i download all the addons i need from WoWI, am i getting wrong version of them or putting them in wrong as well?

thanks for any help with this. i know i'm just doing something dumb but i don't know what it is. lol