Unless your're a full on beginner to music and instruments with no clue how to learn, you can get good information from Free online tutorials. They're everywhere on YouTube. Once you know what specific technique or method you want to learn you just do a search.
If you're super new and have no clue about learning, you may want to set up a list of things you need to learn first to progress.
Here's a guide to follow.
1) learn the parts of the bass, and how it works.
2) learn how to hold the bass, and how to pick and fret the notes.
3) learn more about various ways to hold and pick the bass, and how to fret the notes.
4) learn the basics of music, and basic notation or, the major notes on the fret board.
5) practice and practice on a regular basis
6) the direction of what you want to learn or know will be up to you at this point. And you can find the answers for free online.
Eventually, you'll find a online resource that meets your needs, and teaches the way in which you can learn.
There is no best online instruction for everyone, as everyone's needs and learning ability is different. That's why, you should find one that fits your liking.