To obtain 11.3 SP2 the following steps should allow this.
1 Navigate your browser to support.ca.com and login using your credentials.
2) Click on Download Management
3) Search for CA Workload Automation DE
4) Scroll down to the "Product Downloads" and look for "CA Workload Automation DE MULTI-PLATFORM" which will likely have Version 12.0 listed
5) Click on "CA Workload Automation DE MULTI-PLATFORM"
6) At the top right on this new page, hit the down arrow next to "Release" and choose 11.3. and in "Service Pack" select SP2