If you have a distortion, overdrive, or wah pedal, we recommend having it routed between the guitar and the amplifer  input. If you have another pedal effect (like a delay or chorus) or even a multi-effect device (like the BEHRINGER FX2000), follow these two steps to connect them into the FX loop:  
1.) Plug a cable from the FX Send port on the amplifier to the input of the external effect.
2.) Plug a second cable from the output of the external effect to the FX Return of the amplifer.