It's a pleasure to have you here, @StaceyHZ. Let me guide you to merge accounts in QuickBooks.

If you're using two similar accounts and want to combine them into one, you can follow the steps below. Please keep in mind that the merging process is not reversible.

1. Go to the Settings ⚙ menu and then choose the Chart of Accounts.
2. Find the account you want to keep and then select the dropdown ▼ in the Action column and click Edit.
3. Copy the name and detail type of the account.
4. Check if the Is sub-account option is marked and take note of the parent account it's associated with.

Now let's handle the duplicate:

1. Go back to the Chart of Accounts.
2. Locate the duplicate account and then click the dropdown ▼ in the Action column and then Edit.
3. Modify the Name and Detail Type so the duplicate account's info matches the account you want to keep exactly.
4. If these are sub-accounts, make sure they are associated with the same parent. If only one is a sub-account, make it a parent account by deselecting the Is Sub-account option.
5. When you're ready, click Save and then select Yes to confirm.

For more information, feel free to open this article: Merge duplicate accounts, customers, and vendors in QuickBooks Online.

Otherwise, if you mean to combine two QuickBooks account (company), the only option we have is to import your company data from one to another. 

I recommend importing your Chart of Accounts first. To prepare your Excel for upload, follow the steps in this article: Move your chart of accounts to QuickBooks Online. Heed to Step 1: Get your spreadsheet ready section.

When it's ready, continue with these steps to upload the Excel file:

1. Sign to your QBO company.
2. Choose the Gear icon.
3. Click Import Data.
4. Select Chart of Accounts.
5. Hit Browse, then search for the Excel file.
6. Press Open, and then click Next.
7. Follow the onscreen prompts to proceed. 

Right after, you can also upload Customers, Vendors, Products and Services, and Invoices. Do this in the order I've provided to ensure your data imports seamlessly. 

Additionally, here's an article you can read to help you manage accounts in QuickBooks Online: Learn about the chart of accounts.

If you have any other questions about this, feel free to drop a comment below. I'll be happy to help you further. Wishing you and your business continued success.