Sorry if newbie question pero how do you drive an automatic?

Our family recently acquired an A/T vehicle kasi. Although, I know some basic stuff about automatic transmission vehicles like nakapag drive na ako before (via test drives sa mga auto show/events). I'm used in driving a M/T transmission na vehicle and yes, medyo naninibago ako with the A/T one. Anyways, na drive ko naman yung car from the casa to our house safely. I know lang naman na you just put it in "D" then magdrive ka na. But let's say if i'm going to climb hills or something steep, sapat na ba na nasa "D" lang? or let's say susulong ako sa baha, "D" lang din ba dapat? There's an "S" option and it's for me to control the gear changes pero I'm quite afraid to use it haha. Nasanay lang kasi ako M/T na I have control over the gears and I really don't think I have to go to driving school again (I learned kasi how to drive using a M/T transmission).

And last thing, may alam ba kayo na magandang article about this? haha I'm really sorry if parang ang basic or parang "huh??" ng question ko