What important event in translation happens after the incoming trna is in place?

Molecules carrying amino acids are positioned in the ribosome's two docking sites.

Explanation:

A ribosome is a molecular machine that coordinates protein assembly.

A ribosome brings together correctly the mRNA, which needs to be translated, and the tRNA, which assists in the translation process, to come together correctly. During translation, tRNA molecules carrying amino acids are positioned in the ribosome's two docking sites. After the translation, the tRNA disassemble and is being reused many times.