I've gotten the LCD to light up, but it's not showing any text. I'm 90% sure the cables are connected correctly but I'm not sure. Also, I didn't solder the pins because I don't have a soldering iron.
Any tips? Also, should I post a picture of the setup?
Axiumin:
Any tips? Also, should I post a picture of the setup?
Absolutely!
In order to take a usable picture, it needs to be taken in outside daylight (but not full sun) showing all pieces of your setup and from a direction where it is possible to trace each wire.
Now you are using the original LCD libraries but nowadays there is a far better one available in the library manager in the IDE itself if you add a library called HD44780. When you do that, you will find fully explained example code in the IDE. You do not need that old tutorial.
One other little detail. A bad error has been propagated in most of the circuits published for these displays. The potentiometer should not be connected to 5 V - "Vcc" - always leave that connection out; just connect one end to ground and the wiper to pin 3 on the LCD. That will make it much easier to adjust the potentiometer so that you see a row of "boxes" on the first line of the LCD - and when your code is working, the correct text. For a 10k potentiometer, that will be when it is adjusted near one end (the one connected to ground).