Create Blog Posts
Please view this link
Create Blog Posts to know how to add a post to your blog.Note :
We have to add an image for featured Image to post to display Image on Blog Home page Box.
More detail about Shopify Blog you can find in following link :
Shopify Blog.
Create Contact Page
Please view folliwng link
Create Page to know how to create a page in Shopify.
To create contact page, create a page with title is "Contact us". In "Template" box, select template is "page.contact".
Create Wishlist Page
As create Contact Page, you easy to create Wishlist page, but on Template box select "page.wish-list"