ok i need to know how to use it...
cause i am a little confused about this....
how do you connect to it...and stuff like that...
could any one help

Are you talking about an external effects loop through a head? If so, your amp should most likely have a DSP send and return output/input that you can connect your FX chain to.

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put a lead in the loop send output-->hook up effects/processors-->lead back into effects return.

Should an EQ + noisegate go in the fx loop, or directly into the guitar jack?

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noisegate I would put directly after your main gain, so in the loop if you use the amps distortion, or after a pedal if you use pedal distortion.
Where the EQ goes is a matter of personal preference, try it out and see what results you like best.

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