To insert a two column table paste the table at its desired location. MS Word will format the table in the column where you pasted it. So, if the table is too wide (the raison d'etre why spanning across two columns is desired), it will appear a bit distorted.
Then place the cursor before the table and insert a
section break (continuous). Repeat this after placing the cursor after the table. Then select the contents of this section (i.e. just select the table). Don't fret if the section is not clearly demarcated from the rest of the document (if you prefer to see the section breaks, just press Ctrl+Shift8; the same combo to hide them). Then convert the section to a single column layout. Your table should now span across two columns.
If you are unable to complete any step(s) mentioned in the previous paragraph, refer to the following links: