Here's how to adjust display settings (e.g., Screen timeout, Background style, etc.) on your Gear S3 frontier / Gear S3 classic.
From the watch screen, press the
Home button
to open the apps screen.
Tap
Settings

.
Tap
Brightness
then turn the bezel to select the desired setting (e.g., 10, 9, 8, 7, etc.).
Swipe up or down to scroll through all settings.
Tap
Auto low brightness
to turn on or off.
Tap
Screen timeout
then select any of the following:
15 seconds
30 seconds
1 minute
5 minutes
Tap
Show last app
then select any of the following:
Within 20 seconds
Within 2 minutes
Within 1 hour
Tap
Background style
then select a background.
Tap
Font
then do the following:
Tap
Font style
then select the desired option (e.g., Default, Choco cooky, etc.).
Tap
Font size
then select the desired option (e.g., Small, Medium, Large, etc.).
Tap the
Home button
to return to the apps screen.