Just go to Settings > Permalinks, select Custom Structure and enter the following:
/blog/%postname%/
That will add /blog/
to the beginning of post names in their permalinks. This will not affect Pages.
Just go to Settings > Permalinks, select Custom Structure and enter the following:
/blog/%postname%/
That will add /blog/
to the beginning of post names in their permalinks. This will not affect Pages.