How can I add a bridge to a custom battlefield?

[Mataputas]

I've seen that the models of the bridges are splitted into 2 parts: end pieces and sections (in data\terrain\battlefield\bridges). But they are not available in the battle editor. So, here are my questions:

1) How do I add these models to the battle editor?
2) How do I make the bridge walkable? any pathfinding requirement? Or just paste the parts there, in order?

Well, thanks in advance.