Hi Admin! I have a mains of 60Amps with 4 branches of 3-30Amps and 1-15Amps. Now, can you give me a hint or guide steps on how to attach or should I say, to tap from the meter source going to the mains Ckt breaker? Thank you

If I read this right... you are trying to tap into the utility feed BEFORE the meter (which would be the source to the meter)... which would be very illegal and very dangerous. The way you worded this question is asking how to bypass your meter to avoid paying for electric use.

If that is not correct...please clarify better what you are asking.

You need to clearly explain what you are trying to do. I have no idea what you are asking.
Also, include your location. Your terminology is not consistent with North America, which is where most of us are from. Is this a European installation?