pamac is Manjaro’s installer for both Official Repo and AUR. Or you can just use pacman in the terminal.
We also have pacui, which is a TUI. It is a pacman wrapper, I use it a lot.
If you need to install from AUR, you can use pamac or one of these AUR helpers, such as pacaur or yay. pacaur and yay also can be used in pacui; pacui automatically uses them if they are installed.