How do i connect two portals/chests?

You can't ... because I broke the GUI in the recent updates :( It's getting kind of a problem due to the number of features of this mod it's hard to test absolutely everything before a release, plus I keep changing a lot of things. Don't worry things will stabilise a lot towards 1.0, but thank you for bearing with me while I fix things! Fix incoming...

I've released a 0.7.6 which fixes this. Opening a chest will open the target picking GUI and walking through a portal opens the portal GUI ... but only if they're not already linked. To change the target later you have to mine one side to unlink it.