Upgrading maps on a Humminbird

[fishmaster176]

I have a Humminbird 597ci HD Combo GPS/Fishfinder and the mapping is terrible. It shows landmass, but no water depth or names of landmarks. Just land and water. Am I doing something wrong or do I need a map card (Navionics) to give me some detail? This unit supposedly came with "Unimap" installed, but it doesn't mean much to me if it doesn't show anything. I will spend to upgrade if needed, but I'm not sure if I'm just not turning something on in the unit. The instructions are vague and confusing to me. Of course anything with more than an "on/off" switch sets me back. Any advice? Thanks, Fred