Why can I not find or make Chrome my internet browser?

Firefox is my browser. I do a lot of photography so I have no problem with Picassa, Google plus pictures, but every time I try to download chrome I get an error message.
I have ran every computer fix I can that I have, AVG, 360 Total Security and I use 8.1 and although I rarely use Internet Explorer I have all the updates done. I can even download this half circle Chromecast which I never use. I read answers I could find and other's have this problem. Please advise and treat me like a child as i
need slow easy directions, so I don't miss anything. Hubby who spent years as a Computer engineer can not figure it out. God Bless