On the right hand side, the Properties column shows a grid dedicated to your products variants which enable you to modify them very quickly.
In this grid, you can edit information by double clicking relevant cells, then apply changes such as prices, stocks...
Furthermore, you will find an additional grid on the right allowing a fast association of images to your diverse variants. Just a box to check!
The article below will shed some light on images options for your variants (adding, combination...)
In this additional grid, you can also manage metafields as well as locations for your different variants.