To relate contractual documents in the platform repository you must follow the following instructions:
Go to the main menu of the platform on the left side and click on documents.
Find the contract that you want to relate to other documents in the repository.
Right click on the contractual document and select relationships.
Click on new relationship.
Search in add documents, the contract to relate, add it with the + sign.
Give the relationship a name and click save to make your document related to other documents in the repository.