You need to setup a maintenance schedule.

Lots of ways to do it, write your own, use maintenance plans, Ola's maintenance solution, Minion Ware, Red-Gate tools, Quest tools, Idera tools, ApexSQL tools.

Few links below for you to read up on transaction log management, backup & restore, maintenance plans, and my favorite Accidental DBA book helped me out so many times.

http://www.sqlservercentral.com/articles/books/94938/
http://www.sqlservercentral.com/articles/books/89519/
http://www.sqlservercentral.com/articles/books/68380/
https://ola.hallengren.com/
http://www.minionware.net/
http://www.sqlservercentral.com/articles/books/76296/

If it was me I'd go with Ola, but his scripts can be a little daunting, so read the maintenance plan book and go with that for a first pass.