How do I climb the post?

Hint 1 of 10:

The post is too smooth to climb!

Hint 2 of 10:

How would you make it less smooth?

Hint 3 of 10:

You need to carve a foothold.

Hint 4 of 10:

In order to carve a foothold, you'll need something to carve with.

Hint 5 of 10:

There's nothing suitable inside the hold; you need help from the outside.

Hint 6 of 10:

Have you looked at the poster?

Hint 7 of 10:

There seems to be someone behind there.