First, open Cheat Engine and the game you want to hack. There will be a flashing computer icon when you open Cheat Engine. Click it. Find your game process if it is a downloaded, or your browser if it is an online game. There should be several processes that have the name of your browser, so an easy way to find out which is the correct one is to enable speed hack to each of the processes until your game speeds up.
Once you have found your game process, there are two main options on what you can hack in your game. The first option is a simple value hack for Game scores, Game currency, Game text, etc. The second option is a memory hack, which changes the coding in the game, allowing a different effect from an action. This guide will only explain the value hack.
Lets say you want to hack the amount of 'coins' you have in the game. First, type the amount of coins you currently have in the value box. Change the Value Type to All and click first scan. You will likely not find the exact address that changes your coins. Earn a few more coins, then type the new amount of coins you have and click next scan. Repeat until you have 4 or less addresses left. Ignore the fact if any of the addresses' value is not the same as the amount of coins you have Select them all(Ctrl+shift) and click the arrow. Select them all again in the box at the bottom and double click the value of one. You can change them to any value you like to receive any amount of coins. You can do the same for a score in a game.