**You get the VI by following Peebees' quests line; and you'll want to max out the skill. You will also have to wait until the radiation is clear, as you will not be able to get to the areas. I went back after clearing the Aya questline up to when you go to the Vault. You may be able to do it sooner, but I was trying to clear sidequests.**
The best way to get this is with the 'Making an Impression' side quest on Eos. It is given to you by Hainly Abrams. The stages of the questline will make Remnant spawn for your VI to target. Set the VI to a main skill button [I used R1] spawn him before the fight and once it recharges use the skill again while targeted on a Remnant and it will attack. Be sure to move your squadmates away from the fight: I made sure to see the VI attack just in case.
If you miss any during the initial stages, you will fight a massive Remnant Architect and during the stages of the fight he will spawn waves of Remnant [be sure to target it and it is also required]. The one 'missable' is a Destroyer, as it isn't spawned during this questline. You can find one on Eos by exploring or by the 'Ghost of Promise' quest in a vault. It is located straight east from the vault on the lake. When you use the control panel it will open the door on the far end and it will appear. It's not a pushover with both Shields and Armor so be prepared for a fight.
These are the ones required:
1. Breacher
2. Assembler
3. Observer
4. Nullifier *Edit: Be sure the shield is down!*
5. Destroyer
6. Architect