If you're using FORTE Home or FORTE Premium:
In the main menu "Score", select the tab "Layout" and "Margins".
A new window, "Edit Layout", opens.
Select the tab "Spacing".
Within the part "Default Setup", you can edit the amount of measures per stave as well as the amount of systems per page.
At the right side of the "Edit layout" window, you'll find a preview of your layout. The gray boxes symbolize the amount of your systems per page. Please make sure that all gray boxes are within the dotted line of the white page. Arrange for the number of systems and the margins accordingly.
Confirm your choice by clicking "Apply".
If you're using FORTE Free or FORTE Basic:
A window, "Properties", opens.
Select a stave (single click left).
The stave turns red.
Click right, a new window opens.
Select either "Extend Selection to Page" or "Extend Selection to End".
Depending on your choice, your layout editing applies to either the page you're working on or to the whole score.
Back to the "Properties" window.
Select the tab "System".
Enter your desired layout changes.
Confirm your choice by clicking on "Apply."