Get request_token and request_secret from Foursquare

I want to get my access_token and access_token_secret from developer.foursquare.com. I read and used

oauth_key = 'my_key'
oauth_secret = 'my_secret'

oauth = Foursquare::OAuth.new(oauth_key, oauth_secret)

request_token = oauth.request_token.token
request_secret = oauth.request_token.secret

also I have tried;

oauth_key = 'my_key'
oauth_secret = 'my_secret'

oauth = Foursquare::OAuth.new(oauth_key, oauth_secret)

oauth.request_token(:oauth_callback => "https://foursquare.com/oauth2/access_token")

request_token = oauth.request_token.token
request_secret = oauth.request_token.secret

but when I run my project I get "OAuth::Unauthorized (404 Not Found):" error. How can I solv开发者_如何学Pythone it? Does anyone have any idea?