To do this, you need to already be the Administrator for your organisation's account. Then, click on your account name in the top right corner of the screen once you are logged in. You will see an option to "User Management" - select it.
On the following page, you will see all users currently associated with your organisation, and a button next to each user which enables you to "Promote" that user so that they have administrator rights. Click on the promote button for the user you wish to transfer administrator rights to.
Please Note: You can only have one administrator for your organisation's account at any one time - so once you transfer these rights to another user, your user account will lose administrative privileges for your organisation.