The bottom of the chart is your starting chain. The dark circle is where you slip stitch into the first chain - completing that round.
To start the second round, you simply chain 4 and single crochet into the third chain of your starting chain. You'd then chain 3, skip two chains and sc into the next.
To close the second round, you slip stitch into the first chain you made at the beginning of the second round -- and slip stitch into the next two chains of round two.
You are now in the center of the first loop you made on round two.
Round 3 starts with chain 4, single crochet into the next loop from the second round. You close round 3 the same as round 2.
Hope that helps more.