Open your track mixer with CTRL-M. Find BUS 1 channel strip (next to the audio tracks), and press & hold the gray button at the top of the channel. Select your effect. Then, on the audio track you wish to add the effect to, turn up the BUS 1 level knob. Please note the audio channel will still play the dry signal, the wet signal only appears at the BUS 1, so you will need to balance these two faders to achieve the proper wet/dry mix. Or, if the effect has the wet/dry mix itself, you can turn down the audio channel's fader and use only the bus fader for the mix.