Opening the Vault of Glass is located in the Waking Ruins area of Venus, and launching the Raid from orbit will take you straight there. Once you spawn, your first task is getting inside. Don't worry - it's the easiest thing in the many hours ahead of you.
How to open the Vault of Glass solo
Opening the Vault of Glass traditionally involves a fireteam of six people holding three different Vex sync plates against waves of enemy attacks - and you can read more about how to do that further down if you're planning to do things legitimately.
However, even at 390 Light, it's actually possible for a lone player to glitch his or her way into the Vault of Glass, establishing a save point that can be used to bring an entire fireteam in without having to do any hard work at all. Here's how to do it.
First of all, load the Vault of Glass. The Vault is located in the Waking Ruins area of Venus and the entrance is the massive circular door up on the hill. Ignore it for now, though, and immediately summon your sparrow and race off to the right until you reach the narrow S-shaped concrete tunnel that leads to Campus 9. As you speed along, you should see a message that a spire is forming.
Head into the tunnel, and just after the groove in the ground that encourages you to dismount, stop and wait for 95 seconds exactly. Then jump back on your sparrow and race back to the front door of the Vault. If you time it right, the spire will just have finished forming and the door will open, allowing you to enter without firing a shot.
Once inside, head down the tunnels to the first loot chest, but don't open it. Instead, summon your ghost and go back to orbit. Get your friends to join your fireteam. Once all six of you are assembled, load up the Vault of Glass again and you should spawn inside - saving you the trouble of defending the Vex sync plates - right next to the first loot chest.
How to open the Vault of Glass in a group
The Vault of Glass requires great skill and coordination to complete and you get your first taste of that before you even go inside. As soon as your fireteam arrives in the Waking Ruins you need to divide your strength and take control of three Vex sync plates long enough for a Vex spire to form and open the door. That's easier said than done, though, because first you have to fend off waves of Minotaur-style enemies called Praetorians.
Decide in advance who goes where. The Vex sync plates are located left, centre and right of the Vault door, and it's a good idea to put at least one high-level player in your fireteam on each one. If you're all pushing 29 or 30, that's even better. Your very best players should sit on the central plate, in a position where they can intervene to the left and right if things get hairy.
You need to control all three sync plates at once - you will know you're doing it right because a white checkerboard effect will rise up around the plate and the spire in the middle of the Waking Ruins facing the door will gradually take clearer shape. The Vex will come at you from caves on either side of the door, and will also spawn in the grassy areas opposite, so you will need to keep scanning your surroundings for telltale signs.
The other Vex enemies are fairly simple to repel, but the Praetorians have big shields, so if you have upgraded legendary or exotic void weaponry, make sure you keep it handy, and make good use of your Supers too. Do everything you can to hold the plates, but don't worry if you're a bit rusty - outside the Vault you can still respawn freely.
Forming the spire
It will take a few minutes to form the spire, but soon enough the door to the Vault will open and you can all head inside. Once inside, head down through the tunnels and you will soon discover the first loot chest, containing ascendant materials. You can't miss it.
As of the Age of Triumph update there is a new chest in Vault of Glass to find at this point, regardless of which difficulty level you are playing on.
Keep working your way down through the tunnels and then over a short sequence of platform jumps until you are staring down at a large battleground suspended in the middle of an abyss. This is where you will face your first Raid boss: the Templar.