Gear hotkeys: which is which

As of the latest spreadsheet posted to reddit, the Boar Prime may be farmed in Void Mobile Defense missions. The sheet is here, and this is the original /r/warframe post for the drop table. Good Luck!

To build a warframe, you need the blueprint + the 3 required parts (system, helmet, chassis).

Typically, you can by the blueprint with credits from the store. For the parts, you have to fight bosses (they drop the parts).

Vauban parts can only be acquired from alert missions.

When you get warframe parts, go into the forge and craft them (each part takes credits+resources+time). Once all 3 parts are finished, you can start crafting the actual warframe.

On the warframe wiki you can check where to get the parts for a frame.

It's also possible to buy a complete frame from the market with platinum.

Regarding your invenotry: There are different inventory sections and only 2 are limited by space - Weapons and Warframes. You can buy more space with platinum.