Hey!

For B.Arch. entrance examination, you need to focus on your drawing skills, scale and proportion, geometry and other things.

Then you need to prepare mathematics. Algebra, Matrices, Logarithms, P & C, 3D Geometry, Calculus, Statistics and Trigonometry are some main topics.

Then comes the Physics and Chemistry  portion, for that you need to focus on the basics.

And for the general aptitude part, you need to learn sets, relations and mathematical reasoning.

Hope this answer helps!