To trek during your stay in Nepal, you'll need to be prepared:
If you're not really experienced, or even if you are, don't hesitate to train before the trek.
In terms of clothing, you'll need good shoes, warm clothes according to the season, and a sleeping bag for the nights, but don't pack too much.
Find out about the altitude and the problems you may encounter, such as altitude sickness. It's a good idea to make an appointment with your doctor before your trip to get a check-up and see if you have any health problems that could potentially worsen during the trek.
Taking items such as filterable water bottles can be a good idea.
As far as permits are concerned, you won't need to worry about them; the guides will already have all the necessary documents