You might need to configure how many posts would be displayed on posts index page, when users would need to navigate to the next page after seeing a specific amount of posts. This option would also be very useful if you have custom posts layout, e.g. 3 Columns Grid Layout, or 4 Columns Grid Layout, etc. The configuration is very easy.

Go to Appearance > Reading, and there would be "Blog pages show at most" option, set the number to your liking. Done!

Changing number of posts per page for products, portfolio, or other custom post types

Some of SingleStroke's themes integrates with other custom post types, e.g. Primrose integrates with "Products" post type. In some cases, you would also need to configure how many products you would like to display in the "Shop" page. WordPress doesn't have dedicated option for custom post types. So you would need to install Custom Posts per Page plugin. After installed and activated, go to Settings > Posts Per Page, you would find a list of post types along with the option to set the number of posts per page.