I want hierarchal numbered list to look like 1.1,1.2,1.3...... on Word MAC

How can I achieve following hierarchal numbering in column2 in a table in WORD
like my table should look like as follows
column 1. Column2
1. heading1. 1.1 subheading
1.2 subheading
1.3 subheading
2. heading2. 2.1 subheading
2.2 subheading
2.3 subheading

I am also attaching the doc here
I am using Word on MAC
Hope I have explained my self better
thanks in advance