This is something I found on the net and since this forum is in desperate need of some samsung Jet posts

I will post it here. I've tried it with my jet and it works. Game name is the name of the folder you create and you need a .jad file. If its not supplied with the .jar, google for a jad creator.
1) google for TkFileExplorer v2.2 and install it on your computer.
2) close Samsung new PC Studio (yes close it! y don’t it for this)
3) connect jet to PC and choose PC STUDIO usb mode
4) run tkfileexplorer
5) choose right com port and click connect
6) browse to games folder at “User/Mass/Java/Games”
7) create a new folder for your new software (place JAD and JAR files here)

close tkfileexplorer and open keypad on your jet
9) enter: *#6984125*# to open factory menu
10) choose internals
11) enter: *#9072641*# master key
12) choose 6 storage settings
13) choose 3 update java db
14) quit factory menu and go check the games menu.