D-Link DG-102S Quick Install Manual page 10

Click "Save"
Save Changes
After the settings have been saved to NV-RAM, they will become the
default settings for the device, and they will be used every time it is
powered on, reset or rebooted. The only exception to this is a factory
reset, which will clear all settings and restore them to their initial
values, which were present when the device was purchased.
Click on "Save Changes" on the left-hand side menu. This window will appear
prompting to save the configuration.
Click on the "Save
Configuration" button to
save the system settings to
NV-RAM.
The DG-102S will save the
changes and automatically
restart.