I see lots of questions on how to do this – and I just figured it out using the support site:
Portfolio Page Template
This template will display your portfolio and allow you to set your portfolio as your site’s home page.
When you first activate Illustratr, your posts will display in a traditional blog format. If you would like to show your portfolio projects on the front page of your site (like Illustratr‘s demo site), just follow these instructions:
Create or edit a page, and assign it to the “Portfolio Page Template” from the “Page Attributes” module.
Go to Settings → Reading and set “Front page displays” to “A static page.”
Select your portfolio page as the “Front page,” and then choose another page as the “Posts page,” (to display your blog posts).
By default, page title and content will appear. You can hide them if you prefer by going to Appearance → Customize → Theme Options and check “Hide title and content on Portfolio Page Template” option.