DashPay is a decentralized wallet application for the Dash cryptocurrency, supporting the registration of decentralized usernames through the Dash Platform (based on the blockchain DPNS - Dash Platform Name Service). This allows you to make payments using a username (like yourname.dash) instead of a traditional address. The registration process is decentralized, with usernames recorded on the blockchain, ensuring privacy and security. Below is a complete tutorial based on official documentation and user guides, primarily aimed at mobile applications (Android/iOS), as this is the most common way for users. If you need developer-level code implementation, I can provide that as well.