Newb cant get 4x4 to work

I recently bought a '91 S-10 Blazer 4door with 4x4.  I took it through some trails yesterday and I saw this hill I wanted to go up.  The angle was somewhat steep and the dirt looked a little soft so I wanted to put it into 4x4.  I stopped the car, put it in neutral, and tried to shift from 2hi to Neutral down where that lever is, but it was fighting me and kinda making a grinding noise.  I finally forced it into neutral, but it became even harder to put it into 4lo or 4hi.  It made a really bad grinding noise if i tried to put it into either gear, so I gave up and put it back into 2hi.  I didn't get to climb that hill =( but I need to know what I'm doing wrong or if something needs to get fixed.  I don't know anything about cars so your help would be much appreciated.

Can you push down the button on the 4x4 shifter? If not then check out this post:
 
http://www.blazerforum.com/m_97301/tm.htm

Yeah I can press the button down and shift it into neutral, but it doesn't feel like it wants to go into 4hi/lo.  The floor shifter order is 2WHEEL - 4HI - NEUTRAL - 4LO.  I can shift it from 2wheel to neutral but it grinds if i try either 4s.