Start the program "Menu | Setup | Puppy package manager".
Click on the second button. A new window opens.
Click on the first button. You get another window:
On the left side you can see all programs available. On the right side you see the programs already installed. Mark in the right list the program, which you would like to deinstall. Click on the button "Remove" between the two lists. Afterwards you press the button "OK".
Programs, which are on the Puppy CD-ROM, can not be deinstalled. But you can delete these programs from the menu.