Essentia will not fit into normal cells, instead you will need to craft (and research) Essentia Storage Cells. These come in 4 sizes and hold 12 different types of essentia within them: 1k Cell, 4K Cell, 16K Cell and 64K Cell. These will fit into normal ME drives. Since there are over 48 types of essentia you will need a few cells.
To get essentia into your system you can use ME Essentia Import Bus, these can be attached to your Arcane Alembics to put the essentia strait into your ME System.
You can add acceleration upgrades to the ME Essentia Import Bus, you can also filter what essentia should be pulled in by clicking a bottle of essentia into the middle of the ME Essentia Import Bus.
Now that we have Essentia in the AE system you can view the amounts via a ME Essentia Terminal. This terminal will show all the essentia you have within your system, when hovering over the essentia you can see exactly how much is in your system:
You can add essenica into the system by left clicking Phials into the interface, this will give you the phials back.
The Essentia Storage Bus works just like a normal storage bus, these can be added to jars with essentia, this will show up in your ME system: