First of all there are only a few programs in IIMs they are
IPM after 12th.
PGP/PGDM/EPGP after Bachelors
&
FPM after PGDM or PG.
And since you are still in first year of college you cannot apply to any one of them.
You have nice scores in 10th and 12th but you will need to continue that tradition and bring 90+% or 9.0+ Cgpa in your college overall when you graduate.

Once that is done apply for Cat get a good percentile and then start preparing for WAT GD and PI.

For GD start using newspapers from now on get as much real world info and opinions as possible and the same can be shared while doing a GD.

In PI you should be very clear about your future goal, your SOP for a college your concerned field's subject knowledge General happenings around the world and India and if you by chance have a workex then everything about your workplace and your Role.

Hope this helps.
All the Best.

SMIT-IIM-AMRITSAR-PGP04