uploading website graphics using FTP

I just started using wordpress yesterday….so very new to this. I’m trying to upload grapics to my blog (the header…or theme) using snagit. It asks me for my FTP server, Remote Path, User Name and passowrd. I keep getting a message “The Server name or address could not be resolved.” This is a PNG – portable networks graphics file. What should I do?? Is there anyone I can call for support? Thank you!