There are two ways to position the cursor in EiffelStudio editor: you can use either the mouse or the keyboard.
If you choose to use the mouse, just click in the text where you want the cursor to be moved. If the text is not entirely visible, you can use the scroll bar at the bottom and on the left of the edition zone to display the part you are interested in.
The keys that you may use to move the cursor in EiffelStudio editor are "Home", "End", "Page up", "Page Down" and the four arrows. Pressing "Home" will make the cursor go to the beginning of the line. Pressing "End" will move the cursor to the end of the line. You can use "Page Up" to move the cursor one page closer to the beginning of the text. Pressing "Page down" will position the cursor one page further.
Left and Right arrows can be used to move respectively to the character on the left or on the right of current position. Up and Down arrows allow you to move the cursor to the previous and next lines.