This is an explaination of how to hack a lot of simple games, like most online Flash games (games online on websites like Miniclip and Ninja Kiwi are some examples). Most multiplayer games with the exception of Ninja Kiwi games and some others do not work with Cheat Engine because they are server sided, but if you want to hack a game, try it! The worst that will happen is it will just not work.
Step 1: Download Cheat Engine from www.cheatengine.org/ Your antivirus may say that it is a virus, if this happens disable your antivirus while you install Cheat Engine. The reason is because anything that changes the values of processes can be seen as virus behavior, and on top of that antivirus programs tend to not like anything related to hacking or modifying programs.
Step 2: Open Firefox (Chrome works also but it is much more complicated to find the right Chrome process) and go to your game. If you are hacking an offline game then open that.
Step 3: Open Cheat Engine. It will ask you to allow it to give it admin access. Choose "Yes" for this prompt. Click the glowing computer icon and find the second Flash Player process if you are on Firefox. If you are on Chrome, find the chrome process. If you are hacking an offline game then select that process.
Step 4: Search for the amount of the resource you want to hack. Then go back to the game and change that value (by buying something, for example, if you are hacking money). Go back to Cheat Engine and search for the new value. Repeat until there is only one number remaining in the search results.
Step 5: Double-click the number in Cheat Engine to add it to the address list. In this list, double-click the value part of the number and change it to whatever you want it to be. Then go into the game and attempt to change the value again (eg. buy something). It should update to the new value.