Invoice Plane taken over my home page, HELP!

Hi I have very little coding experience and to say I am a novice is an understatement. The problem I have is I have followed the instructions and invoice plane works perfectly, only my website no longer works as when you type in my web address. It has hijacked my home page. Obviously I have done something wrong, but what?? I don’t know how to fix it. Thank you in advance for your help.

Please follow the instructions described in this post: Unsuccesfull installation