Are the new guns free and how do I get them?

Putting it mildly the in game menu for this "battle pass" is utter **bleep** and makes zero logical sense. How do I unlock the battle pass to start progressing towards lets say, the SOR-300? 

Whoever signed off on this "season pass" menu design, convoluted "tiers", assignments, and cheesy cutscene every time the game loads needs to hang themselves in shame. Your customers hate you and hope you die. <---- That means you're doing something wrong.