Hi there,
You can enable this on a page-by-page basis. So you go to the page in question (here's a link to your About page edit function:
https://steelwheelsblog.wordpress.com/wp-admin/post.php?post=2&action=edit)
Once there, under Page Attributes, select "full-width page template - no sidebar" from the pull-down menu.
If you set your homepage to a static page, you should be able to enable this on your homepage as well (assuming you don't want any sidebar on the homepage).
Cheers!