Welcome back! In the Members Area, under Empires in Arms downloads, there is a PDF tutorial guide to help you navigate the interface. I'm also attaching a copy here. It's a little dated but still useful for getting started.
Please also review the updated user manual for v1.22 (dated 3/20/2018). In addition to corrections and other clarifications since the original manual, there are also player notes and strategy articles in the back. The idea is to maintain all those gems of knowledge from the boardgame experience and help bring new players up to speed. I'll add that the learning curve is steep enough to just figure out "how" to do various game mechanics (e.g., loading troops onto ships to land upon a distant shore, setting a surrender condition after making a DOW, etc.). The manual explains pretty well how to do something.
But the steeper learning curve is figuring out "what" to do with your major power, and every nation has its unique capabilities and limitations. The AI has its weaknesses, but it's good enough for learning the game. My recommendation is to play several short games as each major power and learn as you go. Use the strategy articles as reference. When you are ready, there are pbem games looking to start or adding replacement players. Enjoy!
Empires in Arms Development Team