UOH is my #1 move with Oro, I think about 20% of the moves I use with the intention of doing damage are UOHs. Off the top of my head, here are a few of the situations I use it in.
Use UOH in poke strings after a standing short, mixing it up with cr.mk, cr.rh or st.rh.
Backdash every time UOH is blocked. If it connects you can either backdash to be safe or poke string. Good follow ups after the backdash are st.forward against shotos, st.rh against some larger characters, or immediately dash forward again and throw. Also watch what your opponent does in reaction to blocked UOHs, there are a select few players who like throwing out pokes after a blocked UOH and they all have a hard time breaking that habit, you can probably catch them with a parry 2-3 times in a row.
Wiffed UOH is a good way to bait parries, people often throw pokes out on reaction if a UOH wiffes right in front of them. However, be aware of walk up throws as this is another common reaction.
As Spectre7 already mentioned, abuse the shit out of kara-UOH, nobody is going to expect a high attack from that distance (it’s fucking far) and it will go right over Chun and Shoto’s cr.forward.
Finally, be random, doing a UOH while being pressured in the corner is a good way to catch your opponent off guard, but while stupid shit like that can win you the match, it can just as easily get you the loss, so try to sprinkle a bit of thought into your randomness.