To stake, first you will need liquidity pool (LP) tokens from the pool. To receive those, head to the Exchange/Liquidity tab. In the Liquidity Pool Details panel, enter the amounts of AVAX and AVME you want to send to the pool (when you enter one amount, the other is calculated automatically for you). Make sure you have both enough AVAX and AVME funds, then click on "Add to the Pool" and confirm the transaction. You should now have some LP in your wallet!