1. add custom fields
System> custom fields/ screen>Student Fields Click new.
Add new field to table
system> Page and data management> Manage Database Extentions>
Select table to extend> Usually "Students"
Select "Advanced Extentions"
Next
Select Table you want extention/field to go into
next
Then click next again
Step 4 is where you ad your newly created field
Click "add"
Migrate Data from: Select your fields from the drop down
Assign the field type (string, date, integer, Etc..)
fill out the rest of the form as needed.
Click apply
Then click submit.
Now your field can be used where you need it. :)