You need to have an HDD or Pendrive (formatted to NTFS). Than search a game and download it (from here). Than download Wii Backup Manager Wii Backup Manager (click), plug your formatted Pendrive/HDD to your computer and run Wii Backup Manager.
After your launch it, choose Drive 1, click on Inactive and choose your drive. Than go to Files, click Add, Files add games (in .WBFS or .ISO format), check them and click on Transfer and Drive 1. Copying should start. After it will be done, launch USB Loader GX on your Wii (you can search on YouTube on how to install it if you haven't already) and run the games
I hope I helped you, if you have any questions, feel free to ask