Sub pages

Im not good a code, in fact im an old dog trying to learn new tricks. I love the minimatica, im a photographer so it looks beautiful for my work. I want to add sub pages. I cant work it out.
On my home page if you go into one of my 4 posts, i want each post to have there own second level of choices. currently I cant add a sub page/parent etc to that particluar post, it shows all pages on the right, in all posts.
Idea?

Thanks a lot

D