I have just started using for invoicing on Quickbooks. I added company and customer details, products, number of units but cannot edit rate per item. Can anyone help?

Let's turn on the price/rate option from the company settings, dtelandscaping. 

It must've been turned off that's why you can't edit the item's price. Once done, go back to the item details and add the price.

Here are the steps to turn it on:

1. Click on the Gear icon.
2. Select Account and Settings.
3. In the Sales section, check the Track quantity and price/rate box.
4. Click on Save.

It would also be nice to show the price/rate in your sales forms. To do this, let's go ahead and customise the invoice template.

Here're the steps: 

1. Click on the Gear icon.
2. Select Custom Form Styles.
3. Click on the Edit link for the template.
4. In the Content tab, check the Rate and Quantity box.
5. Click on Done.

I'll also share with you a link containing all articles that'll help you set up your QuickBooks Online. Please check it out: Help Articles for QuickBooks Online.

We are glad to help get your account set up. If you need anything else, please post more questions.