If its the gauged slate that is smooth and not a rough texture you can go over it with pad and carpet as normal. The tack strips will have to be glued and screwed into the sub floor. This will have to be treated as a slab or basement floor installation. Its possible to glue direct the carpet but the slate must be clean and solidly attached. Then you must treat the grout lines so the lines on t show through the carpet. Check all exterior doors to make sure you have clearances. Interior doors can be trimed down. Any questions you can e mail me through my avatar. GL
You poor thing. That stuff was the biggest mistake of the sixties. You need to remove it and replace it with plywood and carpet over that. Sorry.