I'm afraid the blog functionality including our opt-in sidebars are only available when using the OptimizePress Theme version - that functionality is not included in the plugin version
What you may consider doing is using one of our opt-in elements inside your sidebar of your blog using a little workaround that *may* work - depending on your theme
If you go to Pages > Add new inside your wordpress site, and use the "add element" button to create an opt-in form using our elements included with OptimizePress. This will add the shortcode for the form to your page - you can then copy this code and paste it into a "text" element in the Appearance > widgets section - and drop this into your sidebar.
Please note this will only work if your blog theme supports rendering of shortcodes in the sidebars - and also you need to use an appropriate optin form design from our selection otherwise it may not look right in your sidebar