Try clicking browse and load the directory that you have the picture in, and select it if it appears.
If it doesn't, this might be because it's the wrong file type. For example I'm not sure if you can use .jpg or .bmp for an icon, or whether some other dedicated file type is needed. If that's the case you might be able to convert it.
Otherwise I think that a program such as iconpackager would be the only option. I'm sure there are some free ones out there though as well. ?