Step 1. Log into the browser of the D-Link router.Default User Name:admin.Password:(Blank).
Step 2. Select Maintenance and Date and time.
Make sure your date and time is synced to your computer or NTP and is showing the correct date and time.
Step 3. Select Advanced and
Provide a Name for your certificate.
Browse and select key from where you saved it on your computer.
Browse and select the certificate from where you saved it on your computer.
Step 4. Save Settings.
Step 5. Verify certificate is valid.