Is it a must to put grease on the back of pads. I just had my breaks done by my brother and I smell a burning smell on my front right side. Is this going to happen because they are new.

I use the adhesive to prevent rattle. If you had grease on your fingers and got it on the rotor it will cause smoke.
If one side had a pad about worn out and the other one good. I would suspect a caliper hanging up. Be careful the rotor will get hot enough to burn your hand.
If you didn't clean up mounting hardware this also causes problems. This is more of a problem where they use salt on the highway.

Welcome to AF!

Never heard of putting grease on the pads. They reach an extreme temperature and it's the grease you smell burning. It should be taken back apart and cleaned with brake cleaner. If you have a caliper sticking it's OK to lubricate the rails with a high temperature brake grease. If the brakes are making noise it is because the caliper piston is resonating on the back of the brake pads. Like rhandwor says us 3 M brake adhesive on the back of the pads. Do that, or put some aluminum shims between the piston and the pads. Never put grease or oil on brake components.

Thank you for your responses. So the burning smell will go away? The brakes are not squeeling but I do here a very little ticking sound when we drive. All the pads have been changed.

Eventually, the smell will go away if you brake moderately hard for a while. The grease on the pads is smoking.

the only thing realy needed to be greesed is the sliders to prevent the wearing of one pad(the inside one over the other) and your brother either didnt clean your rotors when he touched them or he had stuff on his hands and got it on the pads it will go away but might ake a hot spot on the rotor