I just started off concentrating on the dantian, and after a while I felt like my energy was overflowing, filling the vessels in the legs, and the body in general. I wasn’t able to recognize the tumai-renmai channels, though. I felt at ease.
Then, I started to concentrate on each point as suggested, and after concentrating on the sacrum (in line with my dantien), I felt my energy was very increasing, and my energetic body was different from my phisical body. Like it was going forward. I didn’t know what to do, so I concentrated my attention on the dantian, tried to shrink the energy field, and ended up the session.