@fernandopk You mean HR in general? 
As HR is quite complicated, it's also very different per company, country etc. 

So once you know the basics on the technical stuff on the platform, the best idea would be to work on a HRSD implementation to understand more how HR processes are working or ask your own HR department if you can have a look on how it's currently working. 

I've done several HRSD implementations over the years and every company did things differently, so there is not one way to go, but it really depends on the agreements and contracts.