Need some help Re: Office 365 management

[MyTechSyd]

I run a small IT Consultancy. A new client was passed to me that has their Office 365 managed by another firm. They want me to take over all services, including their Office 365 management.

I need clarification on the following:

1/ Do I need a specific Microsoft Account to manage their Office 365?

As in some type of Admin account.

2/ Do I need an Admin Portal? and if so, how do I set this up?

3/ If there Office 365 was setup by that business, do I need to transfer it to my management, as in my managment area (Admin Portal)?

Its been about 3 years since I managed Office 365 and I cannot remember how I used to access this.

I have only really managed personal users for the last period.

I would really appreciate some clarification on this.

Thanks

[#2]

@MyTechSyd 

1/ Someone who has access to their O365 portal needs to create you an account.  I would suggest calling it something like "admin.xxxx@domain.onmicrosoft.com", and include some random numbers after the "xxxx", so that the account name is hard to guess.  Also, make sure you set up 2FA immediately after it's available, to secure the account.

2/ No; you'll login into https://portal.office.com and then use the above account.  That will let you access the management portal for their instance, since your account name will contain their tenant name. 

3/ No; again, after someone sets up your admin account in their portal, you'll use that to manage their tenant in a browser.  There's nothing for you to setup, install, etc.

You might consider taking the 365 Fundamentals and Azure Fundamentals courses, as they're not only a good route to a basic understanding of both platforms, but both are perpetual certifications and show that you at least know the basics of managing both products.

[#3]

@BinaryWeapon 

Thanks so much for the reply, and the details. Truly appreciated.

I do have one issue. The client gave me admin@domain.onmicrosoft.com

account details, but when I go to attempt to login to the portal, it says the account doesnt exist.

Is there anything the other company may have done to stop the login?

thanks