ZoteroBib is a free, easy to use, online tool that you can use to create a reference list from thousands of citation styles. It is suitable for everyday use for assignments or reports. There is nothing to download, you can start using it straightaway. ZoteroBib is available here.
This guide will show you how to use ZoteroBib. Each page has a short video. You may want to begin by watching them all in order and then return to any of the videos that you want to repeat. Use the menu on the left hand side to view pages within the guide.
If ZoteroBib doesn't sound right for you, you might want to consider using Zotero instead. Zotero is free advanced reference management software that you can use to collect, organise and cite research. It is suitable for managing a large number of references or collecting research over a long period of time. Zotero is available here.