When all the stitches are gone from the left-hand needle, how do you continue? Actually, it's very easy and it's a concept called turning the work.
All you have to do is flip the work over. The side that you just had in front of you becomes the back temporarily. Move this needle from your right hand back to your left hand and you'll see you're right where you started again.
Repeat all the above steps to continue to knit this row and the next and the next. Now you're really knitting.