A DE filter is similar in operation to a sand filter, except that instead of semi-permanent sand as the filter media a DE filter uses replaceable DE as the filter media.

When you backwash a sand filter, you are running the water 'backwards' through the filter and pushing the gunk out of the sand and out the backwash pipe/port. The sand stays in the filter (hopefully).

When you backwash a DE filter, you are running the water 'backwards' through the filter and flushing the gunk and the dirty DE out the backwash pipe/port. After you are done backwashing and reset the valving for 'normal' operation, you then have to add new DE to the filter.

If you're OK with the start-up of your old sand filter, you should be OK with starting up the new DE system. Just remember that the filter isn't filtering until after you put the DE in.

On my DE filter, if the filter is not filled with water, I'll open the air bleeder valve manually when I start the pump until I get some water into the top of the filter tank and out the bleeder valve. I'll close the bleeder valve at that point, let it run for a little bit (30 seconds, a minute, whatever) and then reopen the valve again and 'burp' out a little more air. After I have water flowing 'normally' through the pump/filter/pipes for a few minutes, then I add the DE into a skimmer.

Do you need anything else? Remember that the DE is just the filter media, the rest of the pool chemistry still has to be taken care of as usual. Bleach, borax, baking soda, acid, whatever.