So followed me this explanation is a simple way:
To begin using this new gadget, go to Layout>click "Add a Gadget" in the section where you'd like the email form to appear.
In the following menu, select "Follow by Email" from the list of default gadgets which will bring up a pop-up box like this:
When setting up the Follow by Email gadget for the first time, a Feedburner Feed URL is created for you. Usually this is based on the name of your blog (so long as this feed name is not already in use).
We can change the name of the feed URL in order to:
Create a new Feedburner account using an alternative feed name to the one suggested
Use the name of an existing Feedburner feed if you have already set up Feedburner for your site
Once added, the Follow by Email gadget will appear like this in the blog layout, using a grey "Submit" button and text input field which stretches to fit the available space:
Drop Your Comments And Questions Below.