A fun way to get to know a few scales, practice with a backing track and then branch out into improvisation once you're used to playing the scale notes.
Take it as sloooowly as you like, backwards, forwards, in any order - it will sound just as good.
Click below for ukulele scale diagrams and backing . Go here for UBass.
C major C
G major G blues
D major D blues
F major F blues