Since a ukulele only has four strings you obviously can't make a full 11 or 13 chord, though you can suggest 5+ note chords by using the most important notes. Generally, the most important notes are the root, third (establishes major vs. minor "feel"), 7th (especially in the case of a dom 7 chord).
A 13 chord has basically every note in the major diatonic scale - it's not used very much because it's not all that great a sound, generally. A sus chord "suspends" the third up a half-step to the fourth. But a 13 chord has both the 3rd and 4th.
There is little practical difference between an 11 chord and a 9 chord, and it is the dominant 7 that really sets the character of 7, 9, and 11 chords. So, to "suggest" an 11 chord you might use the root, third, seventh, and then either the ninth or 11th notes. The missing fifth is almost completely insignificant.
HTH,
John