how to set the type of application in twitter?

They not using the concept of "application type" (browser / client)
anymore. For an Android application, you probably want to do the full
(callback-based) OAuth flow, so you should specify a callback URL in your
Application Settings (and declare your oauth_callback for each request
token step you make). Now if you wanted to use the PIN/out-of-band flow,
simply enter "oob" as your Callback URL.