Remove the display and battery, using the repair guide appropriate to your model of iPhone.

Liquid damage may complicate disassembly. Beware of cables and connectors that may be "adhered" to other components in unexpected ways.

Be extremely careful if the battery appears damaged or swollen. If the battery shows any sign of bubbling, bulging, melting, or discoloration, gently remove it and place it in a fireproof (glass, ceramic, or metal) container for transportation to a battery recycling facility.

Even if your battery looks fine, you should not reuse a lithium-ion battery that has come into contact with liquid.

See this site for safety guidelines regarding damaged batteries. Make sure to recycle your old battery and other e-waste at a certified recycler.