You can put content features on by selecting one from the Common Features list on the left (if you want to have some text somewhere you need a Text Area, if you want an image you need to put Image somewhere etc.) and then drag and drop them onto your page
You can move things around by clicking on them and dragging and dropping
You can delete an item by dragging it into the recycle bin
You can add a new row to the bottom by clicking +Row
To delete a row you need to first delete all content and then click xRow
You can adjust the size of ech columns by clicking on the line and dragging it to wherever you want
Hit Preview to see how your page currently looks like