uploaded my logo, but it doesn't change

I am using the SImple Catch theme and tried to change my header logo. I uploaded it, but nothing changes. Tried both multi-file uploader & browser uploader. Made no difference. I also noticed that once it uploads it and displays the file name it adds a number to it. and it also shows up that way with the URL link. Is that because it of how many times I’ve tried to upload it and it keeps track of the # of files? Is that normal? It wont match the file name so would have thought it would cause a problem. Tried changing it within the URL link but that didn’t work.
Example: my file name Logo.jpg and it puts Logo8.jpg

Any help is GREATLY appreciated.