Integrating exsiting members into new install of vbulletin.

I have several hundred members in my aMember membership now and want to add a forum for members only.

I will get the plugin for vbulletin for integration.

Question

Will existing amember members have automatic single login once the board is setup?

To rephrase: Will login using the same username and pass as their amember acount be automatic for existing members or will they have to set up their own logins at vbulletin?

Thanks
H