Click Feature

Notice that when you hover over a cell it gets highlighted

If you right click the highlighted cell you can click the "Create Entry" button to be prompted for the information.

Once you have either right clicked the cell you will need to fill out the information on this page.
Select a project and a project task to which this registration will be billed to, write a description of what it was that you did in those hours and then press OK.
Once that is done a time registration will be created.