How do you say "Thanks for the add" in Japanese?

Question

Answer

We usually do not use a Japanese term equivalent to "the add" in this case.  
Popular expressions are:
ご承認ありがとうございます　goshonin arigato gozaimasu. ("Thank you for your approval")
友だちになってくれてありがとう tomodachi ni natte kurete arigato. ("Thank you for becoming my friend")
or in a politer style,
友だちになってくださってありがとうございますtomodachi ni natte kudasatte arigato gozaimasu.

Answer

追加してくれてありがとう。 tsuika site kurete arigatou.
加えてくれてありがとう。 kuwaete kurete arigatou.

i dont know what "the add" is, if you are added to someone's friend list, you can use these.

friendに追加してくれてありがとう。 friend ni kuwaete kurete arigatou.