The document will have the default name (Document1) and will be automatically saved in the folder selected previously. This can be seen in the top left of the screen where it will show the name of the document and "Saved to OneDrive". By selecting this a drop down will appear showing the exact location of the document.
The document name can easily be changed in the File Name box. It will automatically be updated if return is pressed or you click anywhere outside the box to return to document editing. The Word document is now ready for editing and changes will automatically be saved as it is updated.