How to use purchase model, I got the idea of purchase order and pay bill, But the purchase is something which is directly made purchase from a supplier.

Welcome to the Community, chandrasekarvelr.

In QuickBooks Online (QBO), Purchase Orders (PO/s) are created directly to suppliers when you're ready to buy products from them. Before using it, you'll want to turn on the PO feature first. Please follow the steps below:

1. Go to the Gear icon and select Account and Settings.
2. Select the Expenses tab.
3. In the Purchase orders section, select the edit icon.
4. Turn on the Use purchase orders options.
   
5. If you want, enter up to three custom fields and a default message for suppliers. These are optional.
6. Select Save and then Done.

Then you're ready to make PO's by clicking the +New icon and choosing Purchase order.

All you know to know about how purchase orders work in QBO can be found in this article: Create and send purchase orders in QuickBooks Online.

Also, feel free to visit this link where you can gain more tips and articles for future use: Welcome India customers to Global Community.

The Community is always open if you have other questions. I'll be around to help. Wishing you a great day ahead.