(Excuse my chipped nail varnish) First, you need to tune the 1st string correctly to G(4). This is the most important part that will help you tune the rest of the strings.
Personally, the easiest way to do this is just to learn how G(4) sounds by ear. However, if you can't get it exactly, just guesstimate it as well as you can and you can always tweak it afterwards.
Next, you need to find the 7th fret of the next string down - C(4).
While plucking the 7th fret of the second string with your right hand, tune it up or down until it sounds about the same as G(4).
The rest is pretty much the same sort of thing!
Once you have C(4) properly tuned, hold down the 4th fret of the C string and again, keep plucking the 3rd string while changing the tuning until it sounds the same as the C string with 4th fret held
This string is the E(4) string.
Finally, hold down the 2nd fret of the 1ST string and tune the last string accordingly. The last string is A(4).
Don't worry if you find it difficult to get two strings to sound exactly the same when tuning, i found that it does take a bit of practise 😊
Thank you for checking out my guide, hope you enjoyed it and hope it helped ^-^
- A ukulele