how to switch satellite selection?

Hi. Just had Directv installed with a HD dish. I have a hd receiver, hd dvr and standard receiver. The installer gave me a 18" dish so that I coud take it with me in my camper. He told me I would have to go into 'settings' to change my dish selection from HD to round 18". Figured I'd try it out today. When I hooked up my receiver it just keeps searching for signal. I tried going into settings, but it won't let me do anything. Does the receiver have to be hooked to the HD dish and changed from there? Thanks!