need moar wisdom!
Yes, your wisdom is too low (for now)
As a ranger, level 4 and 5, your 1st level spells per day are Zero (0)
plus whatever bonus spells a high wisdom (14+) would grant you.
this means that you will only be able to cast ranger spells at level 4
and 5 if your Wisdom is 14+.
Also, you will only be able to cast spells up to: Wis -10, so unless
you increase your wisdom, you will not be able to cast 4th level
spells.
Personally, I think that a basic Fighter or Barbarian would be good
beginning classes for novice gamers... I found that spellcasting is a
bit tough in NWN, especially attack spells, because it is real-time
you have to time/center the spells and the targets are moving (for
example, fireball - cast it on an area and the targets may leave by
the time the spell gets there, cast it on a single target and the
other targets may move out of range).
Ranger is a good choice because most ranger spells are buff/protection/
summoning types of spells.
Another idea, you could read the manual that describes the class
features. If one didn't come with the game, it should be on PDF on
your disk. You could also read the D&D 3.0 Players Handbook (should
be cheap on eBay, as a lot of these were dumped when 3.5 came out, and
4.0 is out now) - though some of the NWN rules are different than D&D.
You can also read about the class features in the SRD (Systems
Reference Document) which is available free on the web; but again the
NWN rules are slightly different.
Also, you may want to download some of the free modules from the NWN
Vault - there are many good ones (the Hall of Fame is a good place to
start) and there are some Ranger-specific ones, if you like playing
rangers.