I use navionics on an iPhone – challenging my increasingly long sight to its limits – mainly for reference, planning, and occasionally to give myself a bearing or, to negotiate potential reefs/rocks. Fundoctor has used the navionics to give a course to steer, but I think he’s away at the mo.
As far as I know what you need to do is input a route (could be as simple as where you are now and your next waypoint) and then press Start.
good luck with it. Its actually very impressive software (even at the new higher price) but does take a lot of playing around to discover all the features – there don’t appear to be instructions on how to use it anywhere!!