[ In TERMINAL ] 
sudo apt install synaptic
sudo nano /etc/apt/sources.list
########## insert next 2 lines at top of file and SAVE FILE
# MX Community Main and Test Repos
deb http://la.mxrepo.com/mx/repo/ bullseye main non-free
########## 
sudo curl http://teharris.net/mx21repo.asc -o /etc/apt/trusted.gpg.d/mx21repo.asc
sudo apt update
sudo apt upgrade
exit
 
[ click icon to launch SYNAPTIC package manager ]

1. Click RELOAD and then MARK ALL UPGRADES
2. search on "mx-"
3. INSTALL mx-packageinstaller, mx-pkexec, mx-repo-manager
4. click APPLY and close SYNAPTIC when completed

[ click icon to launch MX package installer ]

1. Avoid installing other MX-specific software - it may break things
2. Avoid installing GTK (Gnome) apps
3. Avoid installing some of the heavier KDE QT apps
4. Prefer lightweight QT apps like kolourpaint, ksnip, kwrite, transmission-QT
5. -or- more neutral apps like Filezilla

NOTE: CutefishOS software repositories are currently located in China. Inserting MX repositories at the top of the /etc/apt/sources.list file should, to some degree, speed up software downloads to the rest of the world and provide backup sources when China sites are down or become unavailable to western nations. OTOH, If you live in China, you may want to insert MX repositories lower down to 2nd or 3rd position in the file.