I am having trouble using quick books as i need major 4 things for my business 1. addping purchase bills so that i can check any purchse any time , 2 inventory management

Hi there, @aeh-spares-gmail.

I'm delighted to share with you the steps to add a purchase order to an expense, bill, or check.

Here's how:

1. Select the + New menu, then select Expense, Check, or Bill. 
2. From the Payee dropdown, select the vendor. This opens a window with their open purchase orders.
3. Click Add for the correct purchase order to add the items from the purchase order. They appear in the Item details section.
4. If you plan to bill a customer for a specific item, select the Billable checkbox. Then add the customer you plan to bill in the Customer column.
5. Click Save and close.

You can also check out this aticle to learn more about when to use expenses or bills in Quickbooks Online.

Additionally, you can visit this link to get more ideas on setting up and track your inventory in QuickBooks Online.

Come back to me if you need more help.I'm always around to guide you.