Took brakes off when trying to sort some problems with the bike i need to know how to get the pistons back into the caliper. i have tried pushing them back normally but they seem stuck any ideas would be appreciated.

Before you do push them back make sure they are clean Otherwise you may damage a seal.

Just take the lid off the Brake fluid reservoir and push them back in.

If they won't go then I would be wanting to service the callipers

How do i go about doing that

Hi
I maybe a bit late, but here's some advice. If the pistons wont push back in through the seal,make sure the piston has a coating of brake fluid on it. check the piston for any dirt or pits on the part that passes the seal. Also do this for the exposed part. If you can remove the seals coat these in fluid to, although it is best to renew them if removing. A pattern part from wemoto is available for a fair price.
If this is still give problems the n use red rubber grease on the seal and piston. Only use red rubber grease, in no circumstances use any other from of grease here. Use it very lightly and sparingly. These should cure the problem, but I will highly recommend you fit new seals.

Make sure the bleed nipple is open or it wont go back in.

Make sure all the seals are well coated with oil as well as the piston, they are a snug fit. If they are dry the piston wont go anywhere.

My pistons were severly cacked up, so I cleaned them up with a brillo pad but there was some black gunk that just wouldn't shift so used very-very fine wet/dry sandpaper to take that off - took a few hours to do all of them. Just sat watching tv whilst rubbing away.

I didn't remove the caliper and didn't empty the oil just held the caliper horizontal, and popped out the piston. Then pulled the seals out with a pointy thing and put the new ones back in, the piston hole was full of oil so it was a bit messy but wanted to make sure they all worked even with the old oil. Then when they were all back together and went for a spin and they worked fine bled the system properly with brand new oil.