Sidebar under the posts

Hello. I would like be able to place the sidebar under the articles in all pages of the blog (front page of the blog and article pages) because I want to place my newsletter form. This it is, three colums of articles and the sidebar under them.

I would like to place it in footer, but I know that this is not possible at the moment.

Can you help me to place my newsletter form under the posts, please?

Thanks in advanced,