hmmmm, FTP you say, did you read my post, i stated i had xenforo install the software, i downloaded filezilla and i think i got into my URL but i have no clue as to where or how to get in in.... you say set the path in Style Properties, you do not read my post ether ... i guess there is no basic tutorials on xenforo.... i guess if you not a developer your %$#$ out of luck or you have to hire someone to do it. so much for getting any help here ...
You've got FileZilla, great. You've completed step one of uploading a file. You'll now need to connect to the server. If you don't know your login details, you need to contact your host. Once you've connected, you should be able to drag the file from your local computer and upload it to your server. That's step 2. After that, you'll want to edit the style property. Search the ACP for @headerLogoPath.
Don't forget to copy it to something like my.logo.png, so in case it gets overwritten by an upgrade if you are using the default style.
My suggestion - make a child style off the default (if you are not already using a custom style - and even then make a child style off of the custom style). That way, when you upgrade (either the default style or the custom style) you won't lose your modifications.
Change the image path (ACP -> Style Properties -> General -> Path to images) to pull from the new child style and copy your forum related images into the child style directory you will need to create under the /styles folder - I just copy my parent folder images (and directory structure) over to the child and do all my updates there.