There aren't typically spells for that sort of thing, as a link is a form of a bond which you are wanting to make between yourself and a deity. I'd scrap the spell idea and go about it like you'd normally try and find a deity you'd bond with.
This includes research of said deity, the pantheon they come from, how they were worshiped, what their relationships with other deities were like, what they like and dislike in terms of actions, offerings, etc., what their traits were, what was associated with them, and then going on to try and contact them to see if they would like to form a bond with you (and this can be done in any manner).
It might not be for everyone. as I originally thought was the case for myself. I found this weird, since I had no issues communicating and connecting with spirits. It wasn't until I had an experence with a deity that "coaxed" me into having experiences with other deities. The experiences are often profound once you are forming or already have a bond with a deity and it differs with each person and deity.
Now, in terms of communication, I've broken them down into two basic forms pretty much everything I've come across falls under; omens and mediumship. The omen form is when you take into account things that happen in a significant way that relates to how your deity is reacting to you. The medium form is when you are actively communicating with your deity on a conscious level as one would communicate with spirits (please note that not all communication with entities is verbal).