Hey there! I had one done when I had CIN ii/iii cells in my pap nearly three years ago now. It was like a longer session of a Pap smear except they put some sort of solution that makes spots visible and they look into the vaginal canal with a special viewing equipment. The actual details may be a little foggy since it has been a while that I got it done, but it was quite fast and generally painless. I took some ibuprofen two hours before going in and I think it helped, I was able to go home myself no problem (then again I'm also the one who walked home from the hospital after a laser ablation to get rid of those pesky cells)
Just wanted to say, good luck and it's good to have these tests done to be sure of your health! I have been getting consistently normal Paps since my treatment
hugs