Hi bro this might help
Enabling registrations so people can sign up for a username and/or site using your signup page is as simple as:
Go to Settings > Settings in the network admin dashboard.
Select “Both sites and user accounts can be registered”
Use “Logged in users may register new sites”– if you want to limit site creation to only logged in users using your signup page
We recommend that you consider using the following options to reduce splogcreations on your network:
Use Limited Email Registrations to restrict who can signup to specific email domains
Install Anti-splog plugin
Click Save Changes at the bottom of the page
Adding a link to your Sign-up page on your main site
You need to create a link to your signup page from the front page of your main site so people know where they can register for a site on your network by either:
Using a theme that includes an option to add a link to your signup page
Adding a link to your signup page
Using an admin bar that includes a link to sign up for a site
Your signup page is located at https://example.com/wp-signup.php
Now anyone can sign up as follows using your Sign-up page:
Click on Sign-up link
This takes you to the sign-up page where you sign up for a username only or username and site.
The signup page on a WordPress Multisite install is located at https://example.com/wp-signup.php whereas on a BuddyPress install it is located at https://example.com/register