To do this with an existing SignCut Pro 2 master account, please open Pro 2 and click the Account menu then select My Account. Scroll down to view and click on the Link to Existing Master Account button, enter your email address and password then proceed to Create Link. 
Once done, close the My Account window and open the Account menu to select the Log in to Master Account option. 
Go to My SignCut tab next, and you will now see all of the computers listed under your master account. Click the Link/Unlink (paperclip) icon on your main computer and a new window will appear. 
Locate your secondary computer on the list and proceed to click on the paperclip icon again at the Action column to successfully link it. 
If you do not have an existing master account, please check out this article to guide you in creating one.
Are you more comfortable following instructions in a video format? Here's a link to our Youtube tutorial for your reference.