As the mission begins, you'll have Link and Impa. Soon, the Champions will join the fray. Immediately send them to defend the marked outposts. Daruk is excellent for holding ground against large groups, Mipha can quickly traverse the map and heal, Revali can clear aerial threats, and Urbosa is fantastic for crowd control and stunning enemies with lightning. Use the map to issue commands and ensure each Champion is engaged.
You'll face several enemies, including Guardians. For Guardians, target their legs to stun them, then attack their eye. Alternatively, use Urbosa's lightning attacks to quickly deplete their Weak-Point Gauge. The key here is to keep all your Champions active and engaged, preventing any single outpost from being overrun. Don't be afraid to switch between them frequently to manage threats.