First thing is Shut Down your Mac.
Do NOT turn it back on!
Repeat Do NOT turn it back on!
If the spill is on the Keyboard turn the machine upside down.
Can you remove the battery?
Depends on which Macbook/Pro you have?
The more current Mac Laptops use
Tri-wing Triangle Y Shape Screwdriver to remove the battery
Let the machine dry out.
Remove the bottom case cover and check for bluish green marks on the logic board.
Ground Yourself after the battery is removed.
If you see this the logic board must be cleaned.
These marks are possible damage to the logic board.
After completely cleaning your logic board and making sure the machine is COMPLETLY dry you and see if the machine will turn on.