The effects loop sockets are one for send and one for return, the send goes to the input of your pedals and the return to the pedals output. The effects loop will put the effect on every channel of your amp.
Don't use the
distortion pedal in the effects loop, it will sounds awful. Effects loops are made specifically for chorus, delay, reverb ect for when you want to overdrive the amp, as placing these effects at the amps guitar input whilst overdriving the amp would sound horrid.
So basically, the only way you can use the pedals for what channel you want, is to switch the pedal on and off when you want it on and off.
I hope this helps.