See Extra information on System requirements and prerequisites for more detailed information on what to do in the steps in the Microsoft documentation (System requirements and prerequisites). The steps that include extra information on are steps 2,3,4 and 7.
See Mapping details for standard entities for more detailed information on what standard entities need to be started and some pre requisites before the A365 mappings will be done.
In some cases certain larger tables can contain record count that is over 500.000 records. When that is the case, we face some limitations in the Dual Write initial sync scenarios. In order to bypass this we recommend a way to accomplish this in a relatively simple way.