I asked a friend to accept my request to become a friend on an app, and since she/he accepted my request, I invited him/her to the app's community.
ご質問ありがとうございます。
"I asked a friend to accept my request to become a friend on an app,"＝「友達にアプリの友達申請を出しました」
"and since she/he accepted my request, "＝「そして彼女・彼は私の申請を承諾したので」
"I invited him/her to the app's community."＝「彼・彼女をアプリのコミュニティーに招待しました。」
ご参考に。
アメリカ合衆国 
