I'm looking for books on the influence of media on culture
To find books you will use a catalog. Depending on your starting place go to either the books page or the catalogs page. Choose OWLCat, the catalog of all our books, ebooks, media, etc.
Next, think about your topic. Media could mean all kinds of specific media that you will want to name in searching; or maybe you are certain you want to do "television." On the other hand, culture could mean material culture (handicrafts, technology, etc.) or artsy culture, from hip-hop to ballet. Lots to think about!
Let's start most generally: do a keyword search on media and culture. Because keyword finds every book description with those two words you are going to get a lot of junk, but you will spot some good titles. Click on them to open up the full record. Scan to be sure you are interested and then look at the subject heading part of the record. You will find suject headings to use in subject heading searches, which are more precise than keyword searches.
For your topic, some of the subject headings I found were: mass media and culture; popular culture; and violence in mass media. Do look for yourself; there are more.