To access subscription library content your device needs to be on the SDSU network using a campus internet address. When you are at home, you can use the proxy server to make publishers think you're coming from SDSU. You can tell you are using the proxy server when you see .libproxy.sdsu.edu in the web address, like https://dl-acm-org.libproxy.sdsu.edu/about/content.
Add this bookmarklet to your list of browser Bookmarks, when you are asked to pay for a journal article or ebook click the bookmark to reload a proxied version of the website to see if SDSU has a subscription.
Drag this link to your Bookmarks Bar: SDSU Proxy or right click and add it to favorites/bookmarks
javascript:void(location.href="http://libproxy.sdsu.edu/login?url="+location.href)