The only way to obtain the game right now is by subscribing to the Origin Access program for $4.99/month or $29.99/year. You can access these games from your Origin account:
• Command & Conquer
• Command & Conquer: The Covert Operations
• Command & Conquer: Red Alert
• Command & Conquer: Red Alert: Counterstrike
• Command & Conquer: Red Alert: The Aftermath
• Command & Conquer: Tiberian Sun
• Command & Conquer: Tiberian Sun Firestorm
• Command & Conquer: Red Alert 2
• Command & Conquer: Red Alert 2: Yuri's Revenge
• Command & Conquer: Renegade
• Command & Conquer: Generals
• Command & Conquer: Generals: Zero Hour
• Command & Conquer 3: Tiberium Wars
• Command & Conquer 3: Tiberium Wars: Kane's Wrath
• Command & Conquer: Red Alert 3
• Command & Conquer: Red Alert 3: Uprising
• Command & Conquer 4: Tiberian Twilight