First you have to get the code for the opt in box. If you are using an email service you get the code from their website.
An easy way is to place it in a sidebar widget.
Under Dashboard / Appearance click widgets.
You should see a sidebar widget area in the right column. Click it to open it. The drag a text widget from the center column into the open widget area. Click on the text widget header to open it. Then paste the opt in code into the text widget and click Save at its bottom. Refresh the sidebar on the live site and hopefully the optin form appears.
