Working with Certificates

Question

Ok, here's my issue.  I'm rather new to VB.Net programming still and have been assigned the task of creating an app that will download a file daily from a HTTPS web site.  I have figured out the code to get me to the site and after authenticating with a digital certificate manually download the file.  My question is how do I incorporate the digital certificate into my app so it authenticates automatically when the app is run?
 
Any Assistance would be welcome?