I want to collab but idk how???

You can't. You could make a studio and share assets between you and other Scratchers.

First off, if you're asking a question, then this topic would fit better in the Questions About Scratch forum.
Secondly, if you want to collab, you can create a part of the project you want to collab, then share it, have your friend remix it, then they have it shared and you remix it, etc.
An option for a true collab system is rejected:

The Official List of Rejected Suggestions wrote:

2.1 Adding users to work on projects
Having multiple Scratchers work on the same project would be difficult to moderate not only due to technological limitations but also because it could lead to private messaging; for more information, see #7.1 on this list. This suggestion includes live editing (similar to Google Docs) and other forms of private collaboration. If you would like to work on a project with another Scratcher, you can remix each others' projects.

At the moment, a turn-based collaboration system for shared projects is NOT rejected; you can discuss it on this topic.

simply remix each other's projects :3
also heccit's pfp changed for the 69th time this week?

Maybe you can do this

1. Posting in the Collaboration forum.
2. Remixing each other's projects
3. Collaboration on a Project is rejected

Za Chary wrote:

2.1 Adding users to work on projects
Having multiple Scratchers work on the same project would be difficult to moderate not only due to technological limitations but also because it could lead to private messaging; for more information, see #7.1 on this list. This suggestion includes live editing (similar to Google Docs) and other forms of private collaboration. If you would like to work on a project with another Scratcher, you can remix each others' projects.

At the moment, a turn-based collaboration system for shared projects is NOT rejected; you can discuss it on this topic.

4. Suggesting for Turn-Based Collaboration

It is a Nice Question
Scratch On!

There is a good way to collab but you have to trust the other person a lot. When you see them in-person tell them your login info and you can work together but only 1 at a time.

Real_Beluga wrote:

There is a good way to collab but you have to trust the other person a lot. When you see them in-person tell them your login info and you can work together but only 1 at a time.

Don't do this. You are only allowed to share an account with someone else if it's an immediate family member - i.e. a parent, sibling, or child. You can't share an account with a good IRL friend of yours, or even with one of your cousins. Source

how do i collab

if you know them then send sb3 files through like outlook or smth thats what i do