Doomed.io 2 is not a simple game. It is a complex game where you need to craft things from collected resources. So first thing in the game to do is to collect some woods and other resources. You need to create pickaxe first to be able to mine resources. But you will be able to use weapons, ranged weapons and shields. Other than that you can place buildings, traps and other fancy items.
How to Play Doomed.io 2
Use ASWD for moving. Left click on the mouse is to use and item or attack the enemy and left click with holding shift key is to use secondary item. With shift key, you can also sneak. Use Q key to drop items. And use R to sell stuff while E is to mount or unmount turret or weapons.