Instagram for Business

Hello!
I wanted to ask, how do businesses go about setting up an Instagram account?

Here is the situation. We have a CEO/President of the company, but he does not handle any of our social media as he is busy managing the company. Myself and my supervisor (our digital director) manage the FB and Twitter accounts.

Is there a way to set up the Instagram account on the CEO's Iphone and have it so someone else (presumably me) can manage it?

I would set it up on my phone, but it does not seem like a good idea to have it on my phone. I may or may not be in the company in the years to come, our CEO will always be the owner of the business and I feel like it is best to link the account to this email/Iphone.

We have an email that we use for our other social media accounts. I am just confused since it has to be on someones mobile phone.

How do corporations manage their Instagram account? Is the McDonald's account really just set up on the social media person's phone? Is there a way to create a "shared" account that is link to the CEO, but manageable by someone else (presumably me).

Thanks in advance!