There are two ways to run effect- a loop and an insert.
What you are doing now is effectivley a loop, however by running the loop from the masters, you're limiting your control
In the case of the behringer:
Connect your effects units to the output labelëd "FX out" (or similar), then take the output of those units and run it back into another, empty channel. You can then use the "FX" knobs to control how much of each channel goes to the effects loop.
In the case of the macike (or any other mixer), you will usually dedicate an Auxillary out to drive the effects loop. It is usually best to take a "post-fade" auxillary when running effects loops. That way, any change in the main channel fader will also change the output to the effects loop- so if you kill the guitar (for example) it will also no longer run through the effects loop.
Inserting the effects is used when you want to apply an effect to a single channel only (this is ually the case with compressors).
As mentioned above ,you take a y-cable (insert type, not splitter type) and plug it into the "insert" jack on the back of your console. This takes the signal from the mixer, out through the effect, then back in. It will only effect the channel that the insert is plugged into.