Using an Internet search engine, of your choice, enter terms of interest that you want to learn about. For example, try the terms "structured" and "cabling". Also when entering terms some search engines will offer additional term to narrow the search scope.
You might also read a subject article in Wiki, which has additional references. Often Wiki is a good springboard into a subject area.
Since you're entry level, if interested in Cisco, their Learning Network and NetAcad often offer some free courses, often at beginner level.
