To generate a quote, click on the Estimate tab on the opportunity.

• To add a new estimate item, click on the + button at the bottom of the estimate section. In the item name drop-down, you will have to choose an item from the existing list of products. 
• You can then add the desired quantity. Based on the Unit Price and Qty, the Total including tax will get automatically calculated.
• Click on the save button to save the invoice line item and click on the generate invoice pdf button.
• Navigate to the Activity tab to send the quote to your lead.
• Choose the Email template that is setup with the attach quote option.
• After choosing the template with the attached quote, click on the send button.
• Now the Quote is sent to the customer.