Hello,
If it is his/hers first bath, then go with some large space (tub) because he/she may totally freak. start with shallow water that way he/she is very comfortable and allow him/her a place to escape the water complete. (like a dry towel, it will get wet)
I would recommend NO more than than than 85 degrees. (If you do not have a proper form of measurements, go with slightly warmer than luke warm. Human external body temp is like 93 so it should not feel warm to you, but it should have NO chill.)
If his/her aquarium is rather large for him/her than more things is not just nice but nearly imperative. you can add fake leaves, three hides (one on hot side, one on cool side, and one in the middle that is humid), you can get something solid for him/her to climb (if you get it from outside DO YOUR RESEARCH first), and just use your imagination (and the internet).