yes
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You most certainly do!

When someone registers it is up to you to give them permissions to do stuff on a blog-by-blog basis. You can also put them in a group knowing that they will automagically get the group permissions.

how do i do that?

For a 1.10.* blog? I forget. It's been a while since I played there is the thing. Plus I hardly ever think about permissions anymore since I'm my only blogger on my 2.4.0 installation and set up my user perms for my 1.10.3 installations a long time ago. "Set it and forget it" yah?

The manual http://manual.b2evolution.net/Main_Page probably has some good info, and if not you can search http://forums.b2evolution.net/search.php these forums and probably turn up a ton of posts about permissions.