Jvim can be used with both the uum input method of Wnn as well as the X11 kinput2 kanji front end processor. Although uum comes with Wnn, it is not as popular as kinput2. Kinput2 is more customizable and has a nice graphic matrix of possible kanji.
Now the fun begins. The bottom of screen first shows that you are in English input mode
You need to get into Japanese input mode. Press i to get into input mode then press CTRL-SPACE or CTRL-SHIFT-2. The menu bar at the bottom of the screen will change into Japanese:
The top of the screen will have a small Japanese cursor: