made a family of parts. You are about to replace a part in an assembly environment. I would like to change the part replacement to one of the Family of Parts items ... A window for selecting another part will appear.
Are you asking how to do that and get the dialog asking which FOP member to choose?
If so, you just use the Replace Part command, but the part you are replacing must be one of the FOP members for it to bring up the dialog. If it is not an FOP member, then it just brings up the standard Open dialog.