So my car was driving fine until this morning. It all of the sudden is extremely hard to put it into gear, like I have force it but there's no grinding except for when I try to put it into reverse. What could this be?

perhaps the clutch needs adjusted

How do I adjust the clutch? Kinda new to manual transmissions.

For the reverse thing, put the transmission in 1st before you go in to reverse.

the engine stay rod bracket that fits between engine and firewall - on EA81's they can come adrift from the firewall causing this problem. Check to see it is still soild. Can be welded back in place. Pedal boxes also get a bit weak and flex losing pedal advantage

Or could be your clutch cable has stretched to the point it is getting ready to break. Every time I have had to make a significant adjustment on my clutch cable it broke not long after, twice that is. The end of the cable is on a fork on top the transmission. Has two nuts on it, lock and adjustment. Loosen the lock nut and try adjusting at a half turn in at a time until you can shift into gear without any trouble. Then lock it back with the double nut.