Keep in mind that after a lead is converted, it cannot be reversed. A lead is ready to be converted into an account when the lead has moved from being a potential customer to an actual customer. In other words, the first quote opportunity is booking.
From the lead detail page click the Convert Lead tab
To tie to an existing account record (if already created), select the account from the drop down and click Link
To tie to a new account, click Create and enter the new account information.
Quotes can only be booked for a contact tied to an account. From the quote record, the lead can be converted to a contact when booking the quote.
Click Book on the quote screen
In the pop up box, either tie the lead to an existing account (if already created) by selecting the account from the drop down and click Link
To tie the lead to a new account, click Create and enter the new account information.
Once a lead is converted to an account, it is no longer in the leads section.
Ref: C-A03