Double-click on the audio track to which you recorded the Dobro guitar. This highlights the track among the other channel strips, making it easier to identify. If you recorded the Dobro in stereo, group the individual tracks together by clicking "Bus" and selecting "Send to Stereo Bus." Do this for both tracks, then click on the stereo bus track that appears at the bottom of the channel interface.
Click "Tools" and select "Reverb." Select a reverb type from the drop-down menu. The specific names of the reverb types vary according to which audio production program you are using, but they are typically descriptive names, such as "Cave" or "Church."
Click the "S" icon on the Dobro track to solo it. Soloing the track mutes everything else and lets you hear it in isolation.
Adjust the "Time" parameter with your cursor. The "Time" parameter governs how long the decay of the note lasts. Reverb emulates the persistence of sound in a fashion similar to, but distinct from, an echo. Rather than repeating a sound as an echo would, reverb extends the resonance. Set "Time" high for a deep, long-lasting reverb. Set it low for a short, snappy reverb. Long reverbs are comparable to the sound of singing in a large hall. Short reverbs are comparable to the sound of singing in a tiled shower cubicle.
Adjust the "Depth" parameter. This governs the emulated proximity of the effect. Because the Dobro has a relatively harsh, metallic sound, set the depth quite high. This has the effect of smoothing off the harsh edges of the sound. Because the decay of the sound persists, the frequencies of the sound blend into the mix better.
Adjust the "Mix" parameter. This dictates the ratio of processed and unprocessed sound. The processed sound has reverb, the unprocessed, or "dry" sound, doesn't have any. Set the "Mix" high to make the sound of the reverb louder than the original signal. This creates a washed-out, spacial sound. Set it low for a more subtle effect.