Welcome to Community! It's great to hear that you're doing well and have gained a new client. Congrats! QuickBooks Online is a dynamic program for completing your daily bookkeeping tasks with confidence. I'll be happy to provide more information so you're on the right track with your work.
When the client signed up for QuickBooks Online, the chart of accounts would have been automatically established based on the information they provided. With that being said, there's no need to enter the previous chart of accounts. With regards to 'closing the books', it's always a good idea to do this at year end to prevent unwanted changes before filing taxes. This feature will lock the books so no one can edit the data before the closing date. Here's how to close the books.
Let us know if this has been solved and please feel free to reach back out if you have any other questions. We're always glad to assist!