From the homepage screen

• Click on the Company Gear (upper right- see pic)
• Select Reconcile under Tools heading
• Choose the Account
• Now you can Reconcile

Another way to get there is from the homepage screen

• From the blue navigation bar on the left, select Transactions
• Select Registers
• Locate and double click the bank account(or credit card account) to reconcile
• On the bottom left is the Reconcile button.

When you reconcile, it is very important to make sure the difference (at the bottom) is zero amount. Do not go for an Auto Adjustment as that will be automatically posted to Reconciliation Discrepancies as an expense in P&L.

Click on the screenshot below to enlarge it