first, you need to download OBS Live in your browser or Chrome 
when you Finish downloading the OBS Live then CLick To Download OBS If it is done open OBS Live then (open) find the source at the bottom click this Sign (+) when you click that sign then you are going to click the (video Capture device)there comes out says (Create/select source) click (Ok) choose your Webcam name after that back find the plus sign again and click the (Image) there comes out says (Create/select source) then click (Ok) then click (Browse  Image files) then click the photo do you want to A background then right Click the Video Capture device in the source at the bottom left click the filter click the plus sign (+) find the (Chroma Key) pick what is your background green, blue, red, and etc. close then go to the chrome then search the 
OBS Virtual Cam download and open  then back to OBS Live Click the Tools at the Top clicl Virtual cam start  there you have it enjoy