To make your phone work like a contacless payment terminal, there are some hardware and software requirements. What you generally need is NFC technology (NFC sensor) in your phone, which allows to communicate between the phone and payment card.
Then you need an internet connection, application for processing of payments and also a required version of operating system on your device. There are multiple applications for receiving of payments available, so you have to decide which one do you prefer. Some of them are offered by banks, but there are also other similar applications, for example, Samsung has released Samsung Pay Touch app, that can be used for receiving of contactless payments.
Many apps that can turn your smartphone into payment terminal require some charges, so it may be difficult to find one that offers receiving of payments for free. Usually there is a small fee charged per each payment.