how can I insert data from two related tables at once

You need to use a JOIN, assuming the two tables have a field in common, such as an id. This is very basic SQL.

For example:

SELECT t1.id, t1.field1, t1.field2, t2.field1, t2.field2
FROM table1 t1
LEFT JOIN table2 ts ON t1.id = t2.id

That will get all the records. If you want to go into a new table I suggest creating the table first and then you could just do an insert using the select statement above.