After 10th,you have to complete your class 11th and 12th with any group but I think HEC (History Economics Civics) will be useful.
After completion of class 12th,you have to complete your graduation (Any degree).
After completion of bachelor degree,you have to take coaching for an IAS for 1 year.
After coaching,You have to appear for exams (I.e.prelims,mains).
If you have qualified in mains then you'll get a call for interview.
The marks of mains and interview will be added.
If you have got a good rank then you'll become an IAS.
Hope it helps!
All the best for your future!