First, create a Twitter collection within SearchBlox. This collection is only available starting with version 8.0.
Sign up to create an application at https://apps.twitter.com, and make sure you have the following values for the Twitter application:
Access token secret
Enter the above values in the appropriate fields on the Twitter collection settings page.
Then, select Filter as the Stream type, and enter the keywords you wish to track in the Filter with Tracks field.
For example, if you enter:
Filter with Tracks: searchblox, search, elasticsearch
this will index all tweets containing these keywords.
See below for an input sample for a Twitter collection: