You can find a "rent" button under each card on the Peakmonsters market. There you see the daily renting costs, the monthly ROI and the length of the contract. You probably have to pay an escrow price, which will be given half to the renter and half to the owner after successful contract end. If the contract is broken by either party, the other party gets the escrow. You need Peak credits to pay your daily fees. Just load up some Steem in your Peakmonsters profile.