Demo
Look at Jaa's blog.
Direction
1. First, download this hack and unzip file.
2. Upload my.php to the main b2 directory.
3. Point your browser to /path/to/my.php. This file will create a table on the database for your custom field hack. If successes, you should see a line of something like "Table created successfully".
4. Still in the main b2 directory: upload b2fields.php and b2edit.php (overwrite).
5. Go to b2-include subdirectory: upload b2edit.form.php, b2functions.php, b2menutop.txt, and b2template.functions.php.
6. Now, log into your b2 admin panel.
7. You should see a "Custom Fields" link included at the top navigation. Click it.
8. You'll be taken to a new page; b2fields.php.
9. Select "Create Custom Field" and type in the name of the field you want.
10. You should see your new field show up at the top, then click "Generate code".
11. It will give you a code that you need to copy-n-paste it in your index.php template where you want the custom field to show up.
12. Go to "Post/Edit", you should see your new field box right below the Post box.
13. Test the hack. Done.