The Regular main screen, shown to the left below, is the default when first running HMPro. While there is a fair amount of information, this is a good starting point for the new user, as information overload is avoided. After you're somewhat familiar with the operation of HeavyMetal Pro, and assuming that your video is capable of displaying at least 800 x 600 resolution, you'll probably want to take a look at the Veteran and Elite versions of the main screen. One of the most important things on any 'Mech are the weapons, of course. HMPro's weapon selection screen is very comprehensive, allowing you to view all available weapons, or filter them so that you only see the missile, projectile, short, long or medium range, and many other factors.
Full information is always available for each weapon during selection.
The weapon selection screen is shown below to the left. After selecting your weapons, you probably want to take a look at the armor type and distribution. The armor and structure tab has this information, as shown to the above right. HMPro will automatically add the maximum armor possible using the remaining weight, and allocate it for you, if you want. Of course, you can still fine-tune it.