Go to Employee Management :

On tab n° 5, sub-tab LPP : 

Although the most common scenario is one contract per person, it is possible to have up to three at the same time.

Regarding the types of settings, it depends on the type of contract and calculation. (In case of doubt, see here for the settings of the LPP)

In the example above it is a contract type where a table of contributions has been previously saved. This is why the options on the left are grayed out. They are not accessible.

If fixed amounts are involved, make sure that Fixed Amount is activated and simply fill in the employee and employer shares