Input the amount of ALPHA token that you want to stake.
Press OK and confirm your transaction.
Once the transaction is confirmed, click Stake button
Press OK and confirm your transaction again.
When staking for the first time, you have to click Stake twice because the first time is to 'approve' your wallet to spend ALPHA token. Approving a token is a part of the process on Ethereum blockchain.
Note that sALPHA is not a token. sALPHA represents your share in the staking pool that is growing in size from the fees accrual.
Not staking for the first time
As you have approved the token before, you can start staking ALPHA Token by: