The red background is indicating that you have no connectors defined in the svg. Your easiest solution would likely be to import the png (which I have never found to work that well by the way) in to the original bb svg for the part which will have the correct connectors defined then move the connectors to where they should be in the svg. Pointers to a couple of tutorials on parts making which may also help:
edit: it may be most useful for you to upload the part .fzpz file (7th icon from the left in the reply tool bar) so we can see what is happening / missing.