1. Get a jailbroken playstation 3 console.
2. Go to the correct section here on NGU, there are plenty of tools, menus, etc. as well as tutorials on how to use them.
Do you own either a Playstation or Xbox Console that is able to be Jalbroken/J-Tag.
Here is a video on how to install mod menus for PS3. If your new I would suggest start using RTM/RPC tools on GTA 5. Best tools to use are LTS, TotalCurryMan, Kryptus and CodeShark tool.