Do you use a genuine software on device? If so, then you can not. You can not use original software with "downloaded" maps, only with purchased. You must replace software on unit with someone from this forum. Then you can use any map you want with accompanying license.
Educate yourself a little bit, have enough informations at other parts of forum. Start from [Only registered and activated users can see links. ]
Also, if you want more help, tell us about your unit and its specifications (operating system, screen resolution, current software version, etc...).