@ChrisMX3417 You can do it in several ways - via terminal text editor or via GUI text editor - anyway you need root permissions (sudo) to edit /etc/pacman.d/mirrorlist file so I recommend to use terminal. Open terminal and try to do the following:
sudo nano /etc/pacman.d/mirrorlist
Then check your mirror list, uncomment lines or add news as @karasu mentioned. Don’t forget to save file after editing - Ctrl+X and then type “y” and press Enter. After than try to update software again.