This is a great exercise to mix it up and get in some single leg work without actually having to be standing on only one foot. You can use a trap bar if you have access to one as well. Steps outlined are for the standard straight barbell.

1. Stand with a shoulder width or less stance. Step back with one foot about 12-18 inches and begin by hip hinging back. Focus on keeping a slight arch in the lower back, knee slightly bent and pushing your butt as far back as possible.
(I would not take too big of a step back when performing this as it only makes it harder to maintain proper position and tension on the correct muscles.)

2. Keeping the barbell as close as possible to the lead leg, I would not go past the knee on the split stance (B-Stance) RDL. 

3. The back foot should push forward slightly as the lead leg reaches full hip extension and you lock out that glute. 

4. Perform 5-8 reps per leg.

Give it some time and load wise it can be comparable to your bi-lateral RDL.