The steps for signing the DDP service for Colombia on AliExpress are as follows:

Visit the official website of AliExpress or the Seller Center and log in to your AliExpress account.

On the Seller Center page, find the options related to logistics or delivery and click to enter.

On the logistics or delivery page, find the options for the DDP service for Colombia and click to enter.

Carefully read the agreement for the DDP service for Colombia and make sure you fully understand and agree to the terms and conditions.

After confirming that everything is correct, click the Sign Agreement button or follow the prompts on the page to sign.

Depending on the requirements of the page, you may be required to provide some additional information or perform identity verification. Please fill in or upload the required information as required.

After completing the signing, you will receive a copy of the signed agreement or confirmation information. Please keep it properly for future reference.

Please note that the specific signing steps may change due to updates to the AliExpress platform. It is recommended that you refer to the relevant guides and documents on the AliExpress official website or Seller Center for the most accurate and up-to-date signing steps.

In addition, if you encounter any problems or difficulties during the signing process, it is recommended that you contact the AliExpress customer service or technical support team, who will be able to provide you with help and guidance.