I need to add a second checking account. or delete the one I added and add a differtent one.

I'm delighted to help you add another checking account and delete the previously created one, Samantha.
 

To add a new account, follow these instructions:

1. Go to the Gear icon, then select Chart of accounts.
2. Select the New button.
3. Set up the account accordingly.
4. Double-check everything, and once done, hit Save.
   

Furthermore, you can also connect the account to online banking if needed by clicking its designated dropdown arrow under the Action column. Then, choose Connect bank and follow the on-screen procedures.

Meanwhile, you can't directly delete an account, but you can make it inactive. QuickBooks doesn't remove your historical data for an inactive account to ensure you can still access past transactions for accurate reporting purposes. For complete guidance, refer to this link: Make an account inactive on your Chart of accounts in QuickBooks Online.

However, if the account you want to remove is connected to QuickBooks bank feeds, you'll have to match its pending transactions first from the For review tab before disconnecting it.

Additionally, it's essential to reconcile your accounts regularly to ensure you have precise records by comparing your bank statement and your entries in QuickBooks.

You can always drop by again to this thread if you have more questions about adding or removing an account in QuickBooks. We're always here for you.