1. Make sure you are a true Christian first, and believe Jesus died and rose again to makes things 100x easier

2. Demons are like rats, they are attracted to trash, remove the trash and they are much easier to deal with. Target the specific sin they are attached to and deal with it. Repent of it and claim the territory back in Jesus name.

3. Rebuke them in Jesus name and take authority as Jesus has given us to command them to leave once you have completed the first 2 requirements.

Done.. I've been there and done that.