Explain why Georgia's decision to secede was important to the Southern States

It encourage other Southern states to secede too.

Explanation:

Prior to Georgia's decision, The Southern states faced a lot of pressure from the Northern states to stop the practice of slavery. But, the southern states can't really do that since majority of their economy was reliant on the slave labors. At first, the Southern states were afraid to secede due to the fear that all northern states will Unite and occupy them the moment they do so.

Under that pressure, Georgia was the first one that  seceded.

This encouraged other southern states to follow since they believed that they can also form a union among southern states to repel the potential attack from southern states.