To port your alts now requires a little more trickery then from the past, when using the old method you'll get the error "I can't use that" when trying to click on the portal. Now for the new method. This still requires a third party or a second account to group with but doesn't require them to stay online. First get a friend or you second account into a group with you, secondly convert to raid, pass lead to second account/friend and log out to your main. Log into your alt and invite to raid or have friend invite "friend can now log, now go to the same place where your main is located in the world. Now log onto your mage and open task manager "windows machines only", find wow.exe in the process list and highlight it. Now open a second instance of world of warcraft and go ahead and type your password into the pw box for faster login. Now create a portal and at the end of the cast end wow.exe in the process list and go ahead and logon with your second instance on your alt. You will now be able to use the portals again!
Hope this helps some out with porting alts!