Lucky you!
Even if the blade is rusty, it should still give an indication of the edge bevels at various parts of the blade. They tend to be wide (obtuse) near the handle and finer (acute) towards the tip - look at it carefully to see if yours matches or if it has any peculiarities.
A careful clean up with light oil and scotchbrite pad should be enough to see what needs doing and where - the Kuk is, in the UK, primarily a chopper so you won't have to go mad to get a shaving sharp all along the edge - unless you really want to.
Any sharpening system will work as they are normally quite soft steel - if it has the two smaller knives that often come with a khukri, the Karda and Chakmak (from memory so don't take my word for it) one is a small skinning knife and the other is a hard strip of steel for burnishing the edge when it gets blunt in the field - though it takes practise to use it effectively.
Any chance of a photo or two?
Good luck
Ogri the trog