Yeah, tutorial would be ideal but you can start by putting some simple written instructions into the game, that describe the basics of how to play. This should also reflect in gui. The information should be visually hierarchical: the most important information need to be most prominent. Try to visually design the game in a way that minimizes any possible confusion for the player.
For example I'm totally confused about the ranges. They are somehow color coded and I encountered at least 6 colors: white, yellow, light blue, dark blue, ochre and red. There is no information on what any of those colors represent. I only guessed that the enemy is red.
I really dig the mood of the game and I can sense there is some depth to the gameplay. I'd like to defeat that enemy, but every time I try, the confusion caused by visual clutter sets in and I just lose any track of what's happening with my units.
Try to clean up the gui and add some basic instructions, either just text or a tutorial. It'll make for a much more fluid experience.