Index -> Interface -> Fleet Builder -> Fleet Builder Options
In the top middle of your Fleet Builder, there are several options for managing your fleet files.

You can open a New fleet, Save the fleet you're currently working on, Open to view or modify existing fleets, and Delete saved fleet files. Other Options are described in more detail below.
Open Online and Save As Online
Online Fleets are saved not on your computer, but on the server. These fleets are useful if you log in to the game from multiple computers. You cannot modify or save these fleets when working offline. You are allowed only a limited number of Online Fleets.
Click Save Online to save your current fleet as an Online Fleet. If you wish to modify an existing Online Fleet, click Open Online to load that fleet file into the Fleet Builder.
E-mail Fleet
This option opens a window where you can input an e-mail address to send a fleet to. You can browse through saved fleets, or check the Use Current Fleet box to send the fleet you're viewing. If you'd like a brief description or comment about the fleet to be included in the e-mail, you can add it in the comment box.
Print List
This option opens a menu of things to print, including your Current Card pool (which prints out the currently filtered cards), Current Fleet, Current Wants List, and Trade List. The chosen list will be sent to the selected printer.

Validate Fleet
The Fleet Validator is a tool you can use to check which play formats allow your current fleet.
Clicking on the various tabs will display formats for tournaments, including Standard Format. You may click on the name of any format to display an explanation of its rules.
If all the fields in a single row display a green OK, the current fleet is legal for that format. If any field displays a red X, the fleet is not legal for that format. You may click any red X for an explanation of the problem.
Fleet Statistics
This option accesses a series of charts and graphs detailing the composition of your fleet. You can view charts broken down by Cost, Rarity, Card Type, and Nation.