Here are the steps to import your inventory file from Excel to QuickBooks Online (QBO):
Go to the Gear icon and select Import Data.
Select Products and Services.
On the Import products and services page, select Browse.
You'll want to select the Download a sample file for your reference in formatting your list.
Find and select your Excel file. Select Open, then Next.
Map your information. Your Field represents the headers on your spreadsheet. From each drop-down menu, select the one that matches a field in QuickBooks Online.
Click Next.
Select Overwrite all values for each product or service with the same name. Make sure everything looks correct because this can't be undone.