Upgrade options?

Hey everyone.
So, I’ve currently got a Dell Inspiron 15
running an i3 6100U
with a GTX 950m and 2 GB of dedicated VRAM
plus just a single 4 GB stick of DDR4 2133Mhz RAM

I'm planning on upgrading my RAM because whenever I check Task Manager, I see that it's already sitting at 39% usage even when I'm barely doing anything, so I'm thinking about tossing in another 8GB. Does anyone know if there's anything specific I need to look out for, or can I just grab any random DDR4 2133Mhz stick and call it a day?

Just make sure you’re looking at laptop RAM. You need DDR4 SODIMM modules specifically.
As for the frequency, you can't really cheat the system; if you buy something faster, it’ll just downclock itself to match whatever the slowest stick in your rig is running. Honestly, don't waste your cash on anything higher than 2133MHz. It's a total rip-off.