Almost want to say if you have to ask,.....get someone with experience to do it.
That said,....if it's a moderatly priced ukulele it will likely benefit from a basic setup, and is something a player can do if he is reasonably handy and goes carefully while knowing what to look for. I do all of my setup work on just about every ukulele i buy, as i tend to be fussy. As most were bought used, others may have altered the original setup prior to me recieving the instrument, as there is a lot of personal preferences involved that the maker can't know in advance. Even changing string brands and types can drastically change the feel, sound, and playability of the ukulele. Intonation often changes as well among the various string types.
A setup involves getting the string height at a optimum level at both the nut and saddle for your playing style. A strummer will require more string height than a light strummer/fingerstyle technique player. There is a happy medium that will serve most players well.
The best playing action can only happen if the frets have been properly leveled and crowned, and the neck is straight but with a touch of relief when strung to pitch. This is not always the case, especially on moderatly priced instruments.
Do a search on this site in the other forums that deal with maintenance and such(tech support), and you will find specific things to work toward. Often a player can spend the time necessary to set up the ukulele that the factories simply cannot on low cost instruments. You can end up with a fabulous player with just your time involved. A small cost in upgrading materials also can be involved, such as adding a bone or ebony saddle where previously there was a plastic one in place. This can be one of the best "bang for the buck" investments made.
.....and it can be great fun working on your own babies,......