Once you are done customizing your design and adding your content, click Continue at the top-right.
On the Schedule page, click the default "Untitled Campaign" text to rename your campaign. Also edit the Subject and From Name fields.
Be sure you have verified your "from" and "reply-to" email addresses. If you haven't you will be prompted to before you send your email.
On the right, you can decide to send your campaign now or schedule for a later date. When you're done, click Send Now.
You'll be redirected to the Email Details page with your sent confirmation and stats relating to your campaign.