How do you use volume to trade?

Hi, i am trading supply and demand and this strategy really makes sense to me. (Chart out key areas on Hight time frame 4H/1D, then drop down to 15min or 1h low time frame to find entry’s) The problem i have is finding the right place to enter. What tips do people have? i heard volume is great for for this but after all the youtube videos i still dont understand how volume works and what i should be looking out for. Any help would be great Thank you