So, all you need to do is to get some knowledge and practice visualisation and artistic skills. Then, after 10+2 apply for entrance exams in your preferred colleges and institutions.
All eligible students, with or without maths background, can apply for B.A. Fine Arts programme after 10+2. However, a candidate should have special aptitude in this field to qualify.
Generally, an entrance-Aptitude Test is conducted by the institution(s) for admission which includes drawing/painting/modelling activities and simple questions related to arts, art history, general knowledge, etc.
Candidates who have studied Drawing, Painting, or other related subject as one of the subjects in their qualifying examination may get some additional benefits.