Before explaining how to develop an Applet, it is important to introduce what a W3bstream Project is. A W3bstream project is a combination of software functions, event logic, data storage, triggers, environment variables, and all the settings that collectively determine how a DePIN application receives and processes data from devices, generates "data-based proofs" that a Dapp may require, and how it reacts/interacts with the blockchain.
A W3bstream Project is created concurrently with the deployment of an Applet on a W3bstream node, such as through the W3bstream Studio interface. If you don't have a ready-to-use applet, you can start by creating a project based on the "Hello World" Applet, that you can select from inside W3bstream Studio when creating a new Project. Later on, you can replace it with a new Applet.
The link below outlines how to access W3bstream DevNet and create a new "Hello World" project.
Once a project is created, you will find it on the homepage of W3bstream Studio. Click on the project to open the Project Editor area, where you will be able to configure the various aspects of your project.