This is how you're going to tune your bass guitar. You want to get a nice tuner. I like to use Peterson. You plug it in. Your first note is going to be E. On the Peterson, it's a strobe tuner, so you want to play the note until the strobe stops running and it almost sits still. Do the same thing for A. That's sharp so I'm going to tune it down. Do the same thing for D. That's way flat. Right now it's reading A so I'm going to tune it up to D. I'm going to do the same thing for G, and it's way flat. It's reading D-sharp, so I'm just going to up it to G.
You want to tune them again because once you've got them all tuned the neck is going to have moved and the pitch is not going to be the same. Then A. And the low E.
That's how you tune your bass.