SAP Web IDE is no longer available via SAP Business Technology Platform trial accounts. Any references to SAP Web IDE in this documentation are only relevant for you if you have access to SAP Web IDE through a productive SAP BTP account. Please consider SAP Business Application Studio as an alternative. See App Development Using SAP Business Application Studio.
When you start it for the first time, you will see a home screen containing more information about SAP Web IDE.
You now see a folder list with an entry Workspace on the left side and an empty code editor on the right side.
Create your project within the Workspace folder by choosing from the menu or Ctrl Alt Shift N . Enter, for example, myProject as the folder name.