Step 1 - On your iPhone, find and open the Settings app, then scroll down a ways and tap on Passwords & Accounts

Step 2 - Now, tap on Add Account 

Step 3 - Then, tap on Microsoft Exchange

Step 4 - Type in your normal email and password and change or leave the description field. That is a personal preference. 

Step 5 - It was ask you to sign in, or configure manually, tap sign in

Step 6 - Type your normal account password and tap sign in

Step 7 - Make sure all options are enabled and marked green, then tap save. Then, head to the mail app and make sure your email is coming through.