You cannot directly link your Best Buy account to Southwest, but you can use the Southwest Rapid Rewards Shopping portal to earn points on your tech purchases.
You generally cannot add a past Best Buy purchase to your Southwest account; you must use the portal link at the time of purchase.
High-demand items (like certain gaming consoles or Apple products) are sometimes excluded from earning points through the portal. Always read the "Terms & Conditions" on the Southwest Shopping site before buying.