To take admission in DMLT in government college, first you check the rule. Mostly you need at least 50% marks in Class 12 Science with Physics, Chemistry and Biology.
After you are sure you fit the rule, you can apply by going to the official website of that government college or university.
Most government colleges give admission by merit. You must check the last date, what papers needed (ID, mark sheet, photos), and if there is entrance exam, so you don't miss it.