If you go into the menu on the top left, the long and latitude appear on the top right hand. If you press this, it says only available when the app. Is purchased.
From what I remember on my phone and tablet apps, I can dial in a long and lat to mark a postion anywhere, but this is slow, or use the hair lines in the centre of the chart. This would involve bringing anything I wanted to mark, hence get the lat. plus long, into the cross hairs and then save it.
Because the app mapping and sonar are similar to my Platinum Plus plus charts on my main plotter, I tend to use it at home to check out an area or as a back up to the main plotters.