I was watching the FSU/Wake Forrest game last night
and FSU had a runner on 1st with 3-1 count on the batter. The runner breaks on the pitch and the catcher throws to 2nd and the 2nd baseman misses the
throw, ball goes to CF & the runner advances to 3rd.
The umpire calls the pitch ball 4 and batter walks.
After the play the announcer says there was an error
on the throw and runner gets credit for a steal.
How does he get credit for a steal when the batter
walked? Just wondering if it is a steal.

Well, fortunately that is a NCAA game, and the NCAA rules explicitly cover stolen base attempts on a walk.

Rule 10 SECTION 11. a. A stolen base shall be credited to the base runner whenever he advances a base unaided (such as by a base hit, fielder’s choice, putout, error, balk, base on balls, wild pitch or passed ball). A stolen base shall be credited when a runner starts for the next base before the pitcher delivers the ball and the pitch results in what would otherwise be scored a passed ball or a wild pitch.

So there is no stolen base.

NFHS and OBR rules don't explicitly call out walks, or other awarded bases. However, it seems clear that runner who advances "without liability to be put out" can't steal a base.