Hii Abul,

The admission for ba honours in Sikkim will start after the declaration of board results that is may so the forms will be out after a month of exam so you can fill the form when the forms will be out(April).In the college's of your interest.

Some of the good colleges are

. Sikkim University

.Nar Bahadur Bhandari degree college

. Loyola College of education

. Sikkim Manipal University

These are few of the colleges in Sikkim rest you can apply according to your choice.