In order to make a DeMat account, one has to follow three steps in total. The first step would be to get in touch with a depository who is registered. The second step is to download the forms and to fill up all the details that are requested by your preferred bank. This might include address proofs, bank statement, a copy of national identity card and so on.
After a turnaround time, you can accept your account to get opened. Then, you must nominate your nominee. These are the common prime/major steps that a person needs to follow for opening a DeMat account in most of the places.