How can I merge/link two video clips in Premiere?
MERGING VIDEO CLIPS

To combine video clips there is something called Nested Sequence.

A very powerful technique.
When adding clips to a timeline you are working in what is called a sequence (normally named Sequence 01), drop your two clips into your timeline and rename your sequence 01 to something like 'My day trip to the market'.

Select a different video clip and drag and drop it onto the 'new item' button. Bottom right of the Project window.
That would create ANOTHER sequence which you can rename as your 'master sequence' from what would probably be called 'sequence 02'.

Now you can drag and drop your original sequence like a clip INTO your master sequence. And tada. 

The wonderful thing about nested sequences is you can go back and re-edit it and it would update in all your other sequences where you use it.

MERGING AUDIO AND VIDEO (original answer regarding merging audio and video)

Import your clips into the project.
Select your video and audio clips (so they are both selected)
Right click and 'Merge Clips...'
It will ask to sync on in (start of audio and video) or out (end of audio and video).
Click ok and you would now have a merge file of both your video and audio clips that you can manipulate as a single clip.

Hope that helps.