You can specify this in a readme file, either as a .txt or a .pdf file. If this is a hard gold connector you will need to order this through our Custom Quote service. I would recommend submitting it through that service.
I had a similar query about customised edge connectors and I was wondering what the right way to go about doing this was. However, I wanted to ask if it was possible to include edge connectors that I have already gotten from someone else, they have been modified a little bit for my PCB. I’m hoping this would cut my cost a little.