You can get to the Xero reconciliation screen from a few places:
Directly from your dashboard
From the 'Accounting' tab at the top of the page
From within the bank statements / account transactions
Once you're found your way there, start reconciling your transactions.
If you're unsure how to do this, please contact Support at email@example.com. We offer Xero training tailored for your situation and your Xero subscription package. Alternatively, check out Xero's Learning pages which provides free videos and information topic-by-topic, or their Xero Support section.