The registered user needs to login to the site before posting anything. Either you need to supply a link to the admin area, or you need to use the 'user tools' widget which provides one on your skin. From there, the member simply needs to use the b2evo toolbar or browse the backend as normal.

Since you've already created the group and permissions, then all you need to do is add this link.

Hi, I'm relatively new (Long story) to actually getting deeper into B2Evo Installations.

I'm also dealing with somewhat related issues (Userblogs & Bloglist by the Amaze me team), but I also have been looking at which users can post, besides their own blogs, in other public blogs.

The way I see it done and I'm going in that direction:
In the Group's configuration in the 'blogging permissions' , I've checked "Depending in each blog's permission", then I can go to an specific Blog 'Blog settings', where I have the options to grant users' or groups' permissions to that specific Blog -- The options here for users or groups are (Some) 'Member', 'Not member', 'Contributor', 'publisher', etc.
As to what permission any 'Category' (Member, not member, etc) has, can be defined by going into the 'Layout' (Also in this screen) And choosing "Advanced" (Layout options are: Simple and Advanced)

I think here is where one can fine-tune the categories's permissions that I'd assign to a user or group.

Good luck and hope you let us know how it turns out

PS:

Sorry, left out about 'a link'

I think that once the user has permission to post in 'A' specific Blog, the 'write' link will be visible and active.

Please keep in mind, I'm new at this and I'm still learning, I hope fast.