Just wait or create another transaction with higher fees and broadcast it.
I tried sending BTC, but it's been at 0/unconfirmed since 9AM. It's now 12PM. I included a tax fee of 0.00000591 BTC. Is this normal? Is there any way to speeding this up?
I'm using bitcoin core
0.00000591 BTC is a low priority fee, minimun to get high priority is 0.0001 btc, just wait, it will be confirmed sooner or later
Its 0.0001
BTC/kb.
How would I do that?
Bitcoin core determines it for you as it figures out the size (in bytes) of the TX. Whether this is normal depends on the things you did not share yet. Whoever receives the bitcoins could try "child pays for parent" to speed things up, but there is no guarantee that it works and its pretty advanced currently.
#1 Are you willing to share the transaction id? If so it would be easier for us to help you. If not that is fine as well, we just have to do more guessing.
#2 Regardless of #1: on what setting did you put the slider that goes from fast (1 block) to normal (25 blocks) or did you set a custom fee?
#3 Regardless of #1 or #2 did you extensivly use faucets in the past? This might result in many tiny (in BTC) inputs that make your TX very large.