You can access funds to deploy contracts on the Rinkeby testnet via a faucet. A faucet provides you with "play" ether to QA your contracts in a sandbox environment without incurring significant ETH costs.
You can find popular faucets below:
If you are unable to access funds from one of the faucets linked above, don't hesitate to send our team a message at hello@metacommerce.app. or via our discord and we'll do our best to help you out!