For older versions of Confluence, see CSV To Table for Confluence 6.x Documentation
Start typing /csv and select CSV to Table Legacy
Select the edit icon
You should see the following:
Tick the box if you want the first row to be a header.
Change the separator field if you want to use anything other than ,
Set the Remote Url field to the url of a remote CSV if you want your CSV data to come from there.
Type or paste the contents of your CSV into the "Insert Text" area