Regarding affidavit

Yes. you can very much give private complaint before the court as party in person.. yes. you have to give your affidavit at the end of the complaint.

You can make a private complaint to your jurisdictional magistrate u/s 200 of CrPC.

Check the complaint's format.

Approach the magistrate with the form of complaint along with the necessary documents (proof of your marriage, any evidence you may have as to your spouse commiting adultery, etc) and the list of witnesses (who can give testimony to support your case.) If the magistrate finds no prime facie reason to distrust your complaint, he shall direct you to produce witnesses. If he finds there's a valid case against the accused, he shall issue summons to the latter for examination.