This project is a collection of samples to demonstrate technologies introduced in Magento 2. You will find the most simple extension along with samples that incrementally add features to lead you through a exploration and education of the Magento 2 platform.
On top of that you can find many tutorials if you search "magento 2 create module" in Google
You need to specify the layout for the page.
So add this layout="2columns-left" on the <page> node in hello_index_index.xml.
You can also use 1column, 2columns-right, 3columns or empty.
Best Answer
Well this is a broad question but my best advice would be to check the official Magento 2 samples.
You can find them here: https://github.com/magento/magento2-samples
On top of that you can find many tutorials if you search "magento 2 create module" in Google