Like seemingly everything in Mass Effect: Andromeda, something as simple as swapping out your armor is not straightforward. You cannot swap out weapons or armor on the fly just by going to your inventory menu. Changing your gear requires navigating both the planet you’re on as well as a series of menus.
Where you can change armor
Basically, any time you see the word “loadout” on the screen, you can swap out your gear (and change the color scheme of your Nomad, which we spend an inordinate amount of time worrying about). There are five tabs on these screens, corresponding to weapons, armor, consumables, squad members and the Nomad’s paint job.
Landing on a planet
Whenever you leave the Tempest and land on a planet, you’ll get a loadout screen where you can tailor your gear to match what you expect to face — though tailoring usually just means picking your best armor and weapons and calling it good. There are a couple notable exceptions to this rule: the Nexus, where you stay in your civilian clothes and don’t carry guns, and Kadara Port, where guns are forbidden (though you do get the loadout screen when you leave the city for the Badlands).
Before a big fight
When you’re about to walk into a big fight — usually around the climax of a priority ops (main storyline) mission, you’ll be prompted with a loadout screen. (These can be a welcome sight if you’ve burdened yourself with a less-than-ideal, underperforming weapon that looked really good in the shop window.)
Every forward station you call down to a planet has an option to change your loadout (as well as a research station to make new gear in some cases) on one side.
On the Tempest, you can swap our your gear by going to the loadout station in the airlock — it’s at the back of the bridge on the left side (port side, behind Suvi). You’re going to keep wearing your civilian clothes while on the ship, but this can be a good way to save time when you land on a planet. If you pick out exactly what you want here, you can rush through the landing process.
Changing your armor’s color and Ryder’s casual outfit
Also important to your mission to save the galaxy is color coordination. You can change both Ryder’s casual outfit and armor colors at the wardrobe in the Pathfinder’s quarters on the Tempest. The wardrobe is a panel on the wall to the left when you walk in. (There are two tabs — the first tab is for casual wear and the second tab is for armor.)