It's always nice to see a new face in the Community. I do see that you posted a question on another thread about reconciling. The good news is, you've reached the right place, and I have the tools to help. Below are instructions on how to reconcile an account through QuickBooks Online.
Go to the Gear (Settings) icon.
Under "Tools," select Reconcile.
Choose the account you'd like to reconcile from the Account drop-down box.
Make sure the Last statement ending date starts the day after your last reconciliation.
Look over the Beginning Balance. Ensure that it matches the one on your bank statement. Here's an article that can help you if they don't match.
Type in the Ending Balance and Ending Date as written on your bank statement.
When you're ready to start, press Start Reconciling.
Next, follow the article above (reconcile an account) for the steps on how to finish the reconcile, depending on if your bank is connected or not.