Hi Jan,
This should be fairly straightforward:
from cctbx import xray
xs = xray.structure.from_cif(file_path="my.cif")
This will return you an instance of xray.structure. If you have more than one data block in your cif, you can specify which structure you want to extract using the block_heading keyword (by default it just returns the first structure it can successfully extract from the cif). There is also similar functionality that can be used to extract miller arrays from fcf or hkl formats.
Please let me know if you have any further questions about this.
Cheers,
Richard