From the Global Dashboard hover over Contacts.
Select Assign Trades
Search for or find the company you want to add trades to & select them.
The Available Trades & Assigned Trades will appear.
With the company selected (highlighted) search or select the available trades you wish to assign to that company.
By selecting a trade from the Available Trades table you will notice it moves over to the Assigned Trades table.
TIP: If you want to remove a trade, simply click the trade you want removed from the Assigned Trades table. This will move the trade back to the Available Trades table.