You can set a signing order in the "SEND DOCUMENT FOR SIGNING" dialog. To do this select the "Set signing order" order option.
Each signer will be automatically assigned a number. Immediately after clicking on "SEND DOCUMENT" your document will be sent to signer number 1. After this signer will sign and submit it, it will be sent to the number 2 and so on.
You can define also more complicated workflows by entering order numbers directly in their fields. In the following screenshot, you can see a workflow where your document will be sent in the first step to signer 1 and signer 2, and only when both of them will sign it, it will be sent to signer 3.