Help required for assigning users to groups

[ Moderator note: moved to Fixing WordPress. ]

Hi. I’m just starting out with WordPress and want to create a site where I can invite users to register on my site (they can only register by invitation). Once a user is registered, I can assign them to zero or more user groups.

I then want to be able to create a URL link which has various attributes such as title, description, date and the URL. I can then assign the link to zero or more user groups.

Users can then see a list of all the URLs they have access too (according to the user groups they are assigned to). A URL only appears once even if it is under multiple user groups that a user is assigned to.

Can anyone please tell me which plugin will allow me to do this please? I’m quite lost as to where to start on this. Thank in advance.