Can I add a user if i am on 39 day trial for QB On Line-Essentials (or Plus).

You definitely can, smcburney.

Adding of users is available for both the trial and paid versions of QuickBooks Online. To do this, simply follow these steps:

1. Click the Gear icon.
2. Under Your Company, click Manage Users.
3. Click the Add user button in the upper right-hand corner.
4. Select the user type, and then click Next.
5. If you chose the Standard user, select their access rights and user settings, click Next and then enter their name and email address.
6. If you chose Company admin, enter their name and email address to invite them.
7. Click Save when finished.

Once the user receives the email invitation, let them click the Let's go! link. If they already have QBO log in credentials, let them sign in. If not, they can create their user ID and password. Here's an article for more details: How to add, delete, or change a user's access.

The QuickBooks Community forum is always available if you need more help. Just leave a reply and I'll get right back to you.