This is probably out of the scope of this forum.
The pastebin API looks to be in php, so you'll probably want to learn php and how to use it. A cursory look showed that tutorialspoint may be a good source. I imagine everything else may make more sense after learning this.
My guess is you'd write a php script and put it in the files folder of your project.
Next you'll probably need to read up on Ajax and how to use it. If the scirra manual isn't helpful enough, find a normal Ajax guide online. It also may be useful to google search how to call a php file with Ajax.
That is where it looks like a mess to me. It's not a straightforward chunk of information to digest, but if you dig long enough you may work out a solution that you can translate over.