DC Tax Sale Foreclosure Process

I just bought my first tax sale property and I’m in the process of foreclosing now. One is a lot behind townhouses and the other is a house in a res. neighborhood.
What are my next steps to determine what I can do with the lot (which is zoned CAP R-4 residential) and
2.) What do I need to do with regard to the owners who are occupying the house?
Thanks