It sounds like you've got the procedure correct, but let's see.
First off, were the Redwirez .wav files in a compressed zipped folder? If so, fully unzip them.
When using the Bass Box Editor, you select the drop down arrow next to any of the CAB slots, and you should see:
View attachment 5121881
You select "From File..." and then navigate to and select the Redwirez .wav file you want.
You should then be able to hear the loaded .wav file, but remember the pedal has an "amp/cab" mode 3-way toggle switch, so to hear the .wav IR assigned to, for example, the bottom position slot (8x10 SVT in the pic above), put the toggle switch in the bottom position on the pedal. ( This also selects the "amp" that is paired with the cabinet for the selected position.)
If you're hearing nothing after doing this, can you get sound back by selecting one of the stock provided cabinet IRs?
As for which .wav file to select, you should be fine with a 48kHz .wav 32 bit or 16 bit file. If you don't know what mic or placement you prefer, then you'll be spending some time auditioning. It's all up to your ears. But first, see if you can get a .wav file loaded into the Bass Box.