Sorry again for the delay.
Showing the input on the left and the output (which is the connection to your amp) on the right.
You almost certainly have all of this at present except for R1 and the associated wiring.
R1 allows the signal to come either direct from the input or through the reverb, or any combination of the two.
R1 should be a linear pot, probably around 10k should be OK.
This resistor will also introduce some feedback which may either accentuate the reverb effect or (in the worst case) cause fairly nasty feedback. This will be worst if the input is disconnected.
The idea is that as you turn R1 from one end to the other that there is no change in volume. This can be adjusted by changing the gain of the amplifier module.
This is simple, but if you have problems with feedback, you might need a slightly more complex version:
This is essentially the same, except the LM387 amp is adjusted to get a reasonable level to the output when R1 is adjusted for 100% reverb, then R2 is adjusted to give the same level when the reverb control is turned the other way.
R2 should be about 1k and should be a trimpot. Once it is adjusted you should not need to touch it again.