Salaam Alaikum,
Witr actually means 'odd' and alhamdulillah you can offer just one raka'ah (which is considered to be the minimum). In fact Scholars differ on the issue and various opinions are offered. The two most prominent ones are:
One group says that witr is solely one raka'ah and should be offered as that (i.e one) after praying any number of two raka'aats after Salaatul Isha. Thus once you finish the obligatory prayer of 'Ishaa you can offer more prayer but they should be made up of two raka'aats each. And you can continue to offer as many as you like, however, you need to end it with a single raka'ah to make it odd.
For example:
4 - obligatory 'Ishaa prayer
2
2
2
2
and so on but finish lastly with 1.
Another group holds that while witr is one raka'ah, it should be offered as part of three raka'aats somewhat similar to maghrib. The difference is that there is no sitting for the first tashahud as you would do for maghrib. Again you can offer any number of two-raka'aat prayers before this as you like.
I hope this has helped. If you are still stuck, you should seek scholarly advice from your local imaam, inshaAllah.
Was Salaam