Start by visiting the administrative site for your event and navigating to Companies in the left hand menu.

Click the "+" button to create the Company. Enter the Company Name. You may choose to fill out the rest of the information if you'd like, or you may send the company website URL to the company to populate themselves. We'll be going of the latter workflow in the steps below.

Now visit the People menu item in the left hand side and select Attendees.

Select the "+" button to add the attendee.

Here you may add the representative as an attendee. You may then send the Welcome Email welcoming that representative into the event. If you don't want the rep to see the full event you're building, make sure to make all menu items visible only to yourself or any group.

Now that the representative is added as an attendee, you may associate that representative with their company.

Visit the company in the admin site and add the person or group to the company. Once completed, the person will now have the ability to edit their company webpage.

Now open up your event website and visit the company.

You may select the Share button in the top right hand corner and then send the URL to the representative. They'll be able to access the webpage and select Edit to fully manage their site.