File/Folder Password Protection

I'm fairly new to Sharepoint. I've used it in the distant past, but not at a company-owner level. It's day one... 

I know in order to password protect a file I have to  send it as a link and update the password there. However, I cannot find the setting that opens this option. Where in Sharepoint do I go to adjust this permission setting to open "Anyone with the Link?" Thanks all!