There are two ways,
Easy Way : Take a class, whoever teaching around you these subjects. But the problem here is that its not grantee that you will learn. Its success depend on that teacher, not on you. If that instructor is not enough learned then it may cost you two way, one is you started feeling that its a difficult subject or second you may learn wrong concepts. Hence Its definitely a easy way but not a good way.
Good Way: Buy two books of each subjects, One of local writer books and one is of Standard International writer. Download NPTEL video or suggested video of that subjects. Start watching one by one all the videos, don't be in hurry, be cool, make notes, if you don't understand anything then go to google, search it and read it, If you don't understand then ask that question a platefarm like this. Read first local writer books and surely read international writer books. Because sometimes local writer write his own thing than about that subjects. So be careful. This is definitely takes a longer time but success is grantee. And you will learn definitely. All the best brother. Welcome to word of CSE.