If you are interested in playing notes instead of chords you should get familiar with the concept of Tabs. Easier than learning the notes of all the strings and their fingerings you play from a staff where each line corresponds to a string and the fingerings show your positioning on the string. Here is a nice site with Ukulele Music for Christmas. Enjoy!
In the music for We Wish Merry Christmas note the chords above the staff, the notes on a traditional staff (treble clef) and the tabs below on a 4 line staff. Traditional tuned Ukulele the strings are G – C – E – A. And the first string is the bottom string when you are playing your Ukulele.