- check how html page is structured, focus on form tag
- install FireBug on FireFox browser or use the same built in mechanism if you are on chrome, then with FireBug open go to 'net' tab and check what calls was done to the server when you sumbited the form
- install scrapy and go though its tutorial http://doc.scrapy.org/en/latest/intro/tutorial.html, when you feel comfortable enough check how to use scrapy FormRequest http://doc.scrapy.org/en/latest/topics/request-response.html#formrequest-objects
Enjoy!