Robolovsky There aren't very many options for customizing the Form Manager. If you are trying to change the theme (there are four choices: Vibrant, Dark, Light, Blue), then you can change the default for your Machform installation in the "Settings" tab (if you are a full Machform administrator). Under "System Settings" find "Miscellaneous Settings", under that find the "Default Admin Panel Theme" drop-down menu and choose the theme to be the new default. Then click the "Save Settings" button at the bottom of the page.
To change the theme for just your account, open the "Account" tab. Under "My Account Profile", choose the theme you want from the "Admin Panel Theme" drop-down menu and click the "Save Changes" button.