I was replacing my front brake pads and when I was working on the right calipper one of the pistons popped up and got stuck so I could not push it back. Stupid mistake...

I then removed the calipper to work on the cylinder and i put it back but in the process I lost some brake fluid. I noted that the level in the handlebar master cylinder did not drop so most of the fluid seem to have come from the ABS reservoir. How do I access this and top up the brake fluid before i attempt to bleed the system?

I remember on my 2006 K1200S it was under the seat, but do not know where is it on 2006 K1200GT?

Any tips/suggestions on how to go about bleeding the system is much appreciated.

I found it behind the left side faring

I topped it up. bled the calliper several times until no air could be seen in a clear hose. I kept on topping up the ABS reservoir and i did add a bit on the handlebar reservoir and all is back in business. I am watching my right calliper to see if i have any leaks on that cylinder that i took out and the banjo bolt as I reused the crash washers.

It actually was very easy to overhaul and check the callipers. I may do them completely this winter as i've seen uneven wear on the pads, although this could also be caused by dirty sliding pins.