Does this $275 Southwest Airlines gift card have fees or an expiration date?

The gift card has no fees and does not expire.

How can I redeem this Southwest Airlines gift card online?

After selecting flights and entering passenger information on southwest.com, choose “Apply Travel Funds,” enter the gift card number and PIN, and click “Apply Funds.” If the card does not cover the full amount, you’ll need another form of payment for the remaining balance.