Do you use a PC with Windows? If so, you will have to download additional software to open RAR files. 7-Zip is widely recommended, and it's free. You can download it from this site: https://www.7-zip.org/download.html
If you're a Mac user like me, your options are more plentiful. Popular programs for unpacking RAR files include The Unarchiver, Stuff It Expander, and UnRarX.
If you would like further guidance, please don't hesitate to ask. We're all eager to see Aenaluck's May and June content, and we hope you'll be kind enough to share it with us.