how can I connect the Op Amp to the capacitor
Depends on what you want to achieve. A fully differential charge amplifier simply has two feedback capacitors and a differential input.
how can I connect the two outputs in order to get the same effect?
Basically the same as above. You should have two high pass capacitors and a diffenrential source to use the fully differential OTA in a meaningful way.
You also can connect a single ended source to each circuit, grounding the respective other input and get a differential output signal as well.