FTP error occured. Access Denied. File may not exist or permissionproblems.

First off I just want to say that I am not a web designer nor am I
very competent when it comes to computers. I am working on updating
my works website with pictures from past conferences; however, every
time I try to upload the page to the site I get the FTP error
message. I tried to mimic everything from the past image properties
but it still won't load. I need a step by step instruction on how to
get this page working correctly. Will someone help me!