To clarify a few things:
As for items marked 'SW:something', you're correct in surmising that those are software. First, be sure to notice in the description pane the 'SF:' number. That tells you which system scale the software is for. 0 is for computers carried on your person. 2 is for mechs. Assuming you play with standard content, no other numbers will be encountered.
Next, they must be installed. In order to do that, they must be in the same inventory space as the computer you wish to install them into. For personal scale SW, simply having the comp and 'ware in your character's inventory simultaneously is enough. For mecha scale SW, move the 'ware from the Field HQ to the mech in which you wish to use it. Now select the software, then select 'Install WhateverWare' (it'll be the first menu item), then select the computer you want it in. Unfortunately, the computers will all be labeled 'Computer' in the selection pane. In order to pick out one in particular, you'll have to pay close attention to the ZeG's (capacity) of the available systems before electing to install the 'ware. WARNING: Make sure to remove any software from a computer that is about to be installed or uninstalled, as software installed on a computer which is destroyed in an engineering attempt is destroyed along with the computer.
As for computers themselves, personal scale systems are available at electronics shops, usually as components of data visors and bracelets, media tablets, and so forth. As for mecha scale, you'll find good ones installed in Ramuhs, Vadels, Savins, Rocs, Ovaknights, Chimenteros, and plenty of other mechs. The ones available at retail are passable in a pinch, but are all default mass for their size classes, meaning that they're too heavy.
Next issue: Storage modules. To be fair, this isn't perfectly obvious (well, most things in GH aren't very obvious.) While most modules have labels which include their type name, most storage modules are labeled as 'Pod' or 'Thruster' or something like that. The Dora, Shard, Argos, Phoenix (which has a backpack!) - all are examples of mechs with storage modules.
Finally, a melee mech with four arms? Not really all that silly, exactly, but still at a disadvantage in a battlefield full of ranged firepower.
Hope all that helped - good luck!
So I can just waltz into the Design folder and take PC_equipment.txt apart, without needing to recompile the game or something? Awesome.
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