What does "hook someone up" mean?
The general meaning of "hook up" is to connect two things together. So to "hook someone up with something" means to connect them to something or arrange something for them. In this case, "hook you up with the invitation" means that you connect them with the invitation by inviting them and giving them the details of the invite. This expression is relatively informal. Ex: If you're interested in the job I will hook you up with the details. Ex: I'll hook you up with an employee who can help you find what you need.