Rules for building a mech are available, here.

Google Mech Builder (Must be logged in to use)

How to Build a Mech.

Step 1: Set the Mech Tier, this will determine the number of Build Points, your Tier is equal to the your character level. (I.e. Tier 1= Level 1, etc.)

Step 2: Choose a Mech Chassis, there are 2 initial choices (2 types of Biped and 1 Quad).

The difference between the two is as follows:

• The Bipeds have arms that weapons are mounted on, these can fire in front and a side arcs (left arms will fire front and left arc, right will fire front and right). 
• Quads are more stable, but do not have any arms. Instead of Arms they have a turret which can fire in any direction.

Step 3: Choose a Power Core, Engine, actuators, armour, and computer

• Power Core: This produces the energy to run the mech and stores it. You can have more systems than energy, but will only be able to use in a single round as much energy as the core produces plus what is in storage.
  
  
  
  • A Microfusion C core produces 5 energy a turn, that means it also stores a total of 5 energy.
  • In any turn the Mech can use the stored and available energy
  • I.e. if the core produces 5 energy and it takes 3 energy to move and you have 2 lasers that each use 2 power the pilot can either move and shoot a single laser or be stationary and fire both lasers. If the mech had at least 2 energy in storage it could fire both lasers and move.
  • Any Energy not used will be stored by the core if it is not full.
• Engine: Determines the base speed at which the mech moves.
• Actuators: Determines the strength and dexterity of the mech. Actuators are required and their cost must be paid every round.
• Armour: Armour increases the mech's AC, as the armour gets heavier and the mech increases in size the BP increases.
  
  
  
  • Starting at Mk 5 armour the Target Signature of the mech increases making it easier for tracking weapons to find it.
  • Starting at Kk 9 armour the Speed of the Mech slows in response to the weight.
• Computer: A Basic computer allows the mech to be run, more advanced computers can be added to assist in tasks such as Piloting, Gunnery, or Computers.

Step 4: Add Weapons: There are 3 levels and 2 types of Weapons. Light, Heavy, and Superheavy. In addition there are Direct, tracking, and Artillery slots. 

• Light Weapons: Weapons used by scouts and skirmishers.
• Light Tracking: Strong longer ranged weapons, generally only have a couple shots.
• Heavy Weapons: Can only be mounted in Colossal or larger mechs.
• Heavy Tracking: Long ranged weapons, many requiring an arcing solution rather than direct fire.
• Superheavy Weapon: The strongest of weapons mountable on a mech.
• Superheavy Tracking: Long range tracking weapons
• Artillery: Artillery Weapons are long range and incredibly powerful. Capable of devastating buildings and other mechs in a single shot.

Step 5: Ammunition

Some weapons require ammunition to use. A single magazine is automatically included with the weapon, additional capacity can be purchased for more BP.

Step 6: Other Systems

There are numerous other systems such as shields, ablative plating, thrusters and jump jets, and a variety of mechanism that can customize a mech. It is recommended to spend all available Build Points