Once installed on your computer, open MapSource....select City Select...choose what you want to load (the map titles)...switch your MapSource product over to the Tide product (162/168 Tide Points)...select the tide points transparent maps you want...then save the map set (all at once) to your unit via the save to device function. That way, the tide points and the street maps all get into the unit and coexist there at the same time. I beleive the tide map has 3 selectable areas: East, West and Gulf Coast. The tide points are a transparent map which will overlay your existing maps. Alaska to Mexico is a 51KB download.