How to move a root account to a reseller one?

I have a client using an account with three domains and now he wishes to transform that account into a reseller one and I should move those three accounts into his reseller sub-account. How should I proceed? Tks!

First of all, you must convert the additional domains into individual accounts, you do this from the domain listing in the admin

After this, you can change the root account to reseller, changed only the package, remember that the new package must have reseller privileges

Once you have the reseller account created, you must create the first package from the reseller account.

Change the addon domain account package to the new reseller package

Thank you José,
I have already done steps 1 to 2 but I don't know how to proceed with step 3 and, specially, step 4. Can you kindly give me further help? Thank you again!

Step 3, go to the user panel of the reseller account and create a package

Step 4 from the admin you can assign this new package to the accounts you created for the additional domains

Thank you again, José, for your valuable help.
All the best!