The data needed in the forms can be found in a dialog box.
Click on the "magnifying glass"-icon to open a new window, where you can search for the needed data.
Usually, there is a CODE and a NAME in a dialog box. (For example: when searching for a student, the dialog box contains the student's ID and his/her NAME.)
If you know the CODE by heart, you can fill it in the appropriate field, and the system adds the NAME itself.
For more details see SIS - useful tips
Another way is to choose from a list - see the following picture:
Click on the arrow to open a list to choose the data from.