How to Distribute Loads on DB

Recall ...recall all your mathods and standard ratings. No more fundamental information with me.

Surely you don't expect much of an answer to your question with so little detail, do you? What is a DB (Distribution Board?)? Is this for a home, an industrial or commercial site, other? What other power loads do you have?

Draw it in CAD, take a plot, do it.

List out connected loads to be connected on DB. Connect the Load to DB equally if it is single phase Load on all 3 phases.Always maintain Balance Load on all 3 phases.Remaining rating of DB ,I think you are aware of It.

There are tables giving standard ratings for various loads like lighting-100W,receptacle-90VA etc. Then you should apply diversity and load factors.If you know the actual loads connected you will get very accurate results. The loads should be divided into various circuits(branches)with suitably rated MCB/Cables for each circuit. Making an allowance for future extension you can size the main breaker. Refer BS7671/NEMA/NEC/VDE etc

where can I get those tables?...what is load factor?

You can get tables from electrical items OEM.Load factor=The ratio of average load to Peak load or total capacity of load