Hello @dekaa_momon
You should check the Update Manager documentation on https://documentation.softwareag.com/
Once there, please search for Software AG Update Manager (left upper corner)
For version 10.3 you need “Product Releases October 2017 to April 2019” version of the guide (Update Manager 10.1).
Please, note that you need active Empower credentials and license for the products that you want do download fixes, as they are not generally available to everyone.