Step-by-step:
1. Download the plugin to your computer.
2. Unzip it and open the file bp-export-users.php in a text editor (notepad, notepad++, gedit, etc.)
3. Find these lines: $this->wp_fields = array(
'ID',
'user_login',
#'user_pass',
'user_nicename',
'user_email',
'user_url',
'user_registered',
#'user_activation_key',
'user_status',
'display_name',
'spam',
'deleted');
4. Add the names of any custom WordPress user fields you want in ‘inverted commas’ before the closing bracket ) making sure you put a comma in between the fields. E.g. ‘deleted’, ‘custom field’, ‘custom field2′)
5. Find the lines: $this->bp_fields = array(
'Name',
'Telephone',
'Job Title',
'Organisation',
'Region',
'Primary Discipline',
'Grade',
'A bit about you',
'twitter',
'flickr');
6. Add the names of any custom BuddyPress (xProfile) fields you want to export in the same way.
7. Save the file.
8. Zip the folder.
9. Install the plugin in your WordPress installation using the upload method.
And you should be away.