The payment of the interest comes from the wallet of the contract creator. If you want to create a Staking contract you need to provide the funds for the contract to pay interest to token holders
To approve funds to yhour contract do the following
Screen Cast
Approve funds
Login into your WordPress install.
Login into Metamask with your admin account
Go to your stake page
Click on approve button
Fill in the amount you want to approve
Click on approve button
Confirm you transaction in Metamask
Ube Start and End StakesIf you are using an Almond flavor you need to approve funds for both tokens, the staking token and the secondary token