For civil service exam you need to graduate as per eligibility criteria for exam

if you do m.a then it's not problem you go for it and make focus on subjects liks which is in IAS exam like history , political science, geography etc

and learn it you can go on upsc website download your optional subject previous year question papers and try to solve it

If you need more you go on byju's IAS ,vision etc website and attend sessions which is conducted by him