First of all, you must to study the theory about offshore structures such as environmental loads, static and dynamic behavior, statistical treatment and other things. I recommend to study the Handbook of Offshore Engineering.
If you want to study specific topics in submarine pipelines and risers, the following books are a good option:
Fundamentals of Marine Riser Mechanics (Sparks)
Subsea Pipelines an risers (Yong Bai)
Offshore Pipelines (Boyun Guo)
You could to study some rules (DNV, API, ABS)
Softwares:
For structure: SACS, GeniIE, STAAD
For subsea pipelines and risers: OrcaFlex, DeepC, DeepLines