From your dashboard, you can easily navigate to all "Pending" transactions. If you click on one of these, you will see the screen below:
By clicking on the envelope behind a signatory, this person will receive a reminder email. This email will then only be sent to this signatory. To send a reminder email to all signers, click on "Remind" at the top right of your screen:
It is also possible to configure an automatic reminder schedule for a transaction. When creating the transaction, you set when and how often a reminder should be sent to those who have not yet signed.