It's a lot of work but you get use to it after a while. First off you need to download the newest version of RotateMe.
Samir is the guy who made RotateMe, his website
By Samir Only his newest version of RotateMe can be signed. You have to donate to him to get the newest version.
Next Go to
https://www.symbiansigned.com/ and click Open Signed.
On the next page they ask you for your IMEI Number, simply type *#06# into your phone
Fill out the rest of the information and pick the Application you want signed.
I believe the Signed Application works for 3 Years.
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Now I forget what the deal with the email is but I dont think public domain emails work. (Yahoo, Gmail, Hotmail) You might need to create a private domain email.
I used this private domain,
CJB.NET Its Free. Just click on Free Web hosting.
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If you dont have RotateMe and dont feel like donating right now, For practice of how Signing an application works I recommend you sign FlipSilent. Its free and a really cool application to have anyways.