If you don't already have an Instagram account for your business, you can just follow these steps to create one.
From the Instagram app:
1. Click on Sign up
2. Enter your login details
3. Choose a user name (ideally your company's name)
4. Fill in the necessary information to create the account
Once you have an account, all you have to do is change your account to a business profile. Read this article to upgrade your account to a business profile.