It is possible to populate a managed table directly from an access database, these are the steps.
1. Create a new action step by clicking on three vertical dots (found to the right of the group's name) and then select "Add action step":
2. Under "Manipulating Data" select "Manipulate Data"
3. Click "Select Instruction Type" and type "Access to SQL table" and add the instruction.
4. Configure the "Copy from Access to SQL table" instruction. Select the Access database and table you want to import into the managed table.
Tips and tricks
Remember, the structure, i.e. the number of columns and data type, in both tables must the be same.