This tutorials teaches you how to link an instrument or a sample to the mixer on and add there a reeverb effect.
1. First left click your instrument. In this case It is FL Keys.
Now let's add an effect on it.
1. Here you can insert effects. Left click it -> select -> and choose Fruity Reeverb 2
Now you can link synths to the mixer and add effects. Just try different effects to figure out what they do.