While we don't offer a built-in blog feature right now, if you need something fairly simple then you could use our Custom Pages feature.
An easier and more powerful solution would be to install the DropInBlog app from the Thinkific App store: this third-party app allows you to quickly integrate blog content into your Thinkific site through a custom Site Builder section. The DropInBlog service also includes some useful content-management tools, including built-in SEO analysis.
It is also possible to use an external blog platform like Wordpress and link your Thinkific site to that using custom links in your header. This is a common solution for many of our customers.