It's literally placing your finger on a button. Tough to remember.
Then color me stupid, because I've never found it that easy. I many times put my phone near the NFC thingie, waited for something happen, nothing happened, felt stupid, and just pulled out my wallet instead -- much faster, feels less dumb and clunky.
It also took me time to figure out how to use it on my Apple Watch -- again, it just felt unnatural, took me time to twiddle with something, orient my wrist strangely... there's really nothing I gain from it over just using a bank card. It felt gimmicky to me.
The only time I've found it super useful is as a backup -- when I have forgotten my wallet -- in which case, I don't care how long or how clunky it feels, I'm just glad I can pay for my stuff.