In the season 5 or 6 last episode, Barney works as taxi driver to pick chicks. But, in the second season,he is so scared to drive the Fierro.
When did he learn to drive?
Well, it is kinda well-explained on IMDb FAQ page,
The thing to keep in mind is that the driving lesson scene in "Arrivederci Fiero" is a flashback to sometime "last year"; if Ted didn't misspeak, that means sometime in 2006. Barney has a car by the Season 1 finale, "Come On," assuming that it wasn't part of some ruse; either way, he's definitely driving by "Brunch," and apparently drives a truck soon after "Arrivederci Fiero" in the episode "Moving Day" (granted, he only drove it a short distance to the back of MacLaren's, but Ted didn't seem to take Barney's supposed inability to drive into consideration).
That leaves a sizable window of time in the first half of 2006 (i.e. the last half of HIMYM S1) in which Barney was able to learn to drive. Given that Barney is both impulsive and obsessively driven (no pun intended), it's possible that he got over his fear of driving and mastered the skill very quickly.