When I lose a battle and make a retreat to the territory of an ally , and how do I remove the drives from there ? And when I do this ?

Your question is a little confusing

You cannot retreat into territory which is owned by another player.

RULEBOOK, PAGE 21:

"The retreating units must retreat to one empty adjacent
area (i.e., one containing no enemy units or enemy Power
tokens) or to a friendly area."

Even though you have made an alliance with another player, with regards to the rules they are still considered an enemy. Alliances are just verbal agreements between players and don't effect the rules at all.

I'm also not sure what you mean by 'remove the drives'.

When I lose a battle and make a retreat to the territory of an ally, and how do I remove the drives from there? And when I do this?

Units from different Houses, irrespective of verbal agreements or alliances, can NEVER occupy the same space in AGoT.