Question Download Required Resources from Web Server

I have around 250 rose image assets and I want to keep these in different resolutions so I can load them as per device capacity.

For high-capacity devices, I want to load high-resolution roses images and for weaker devices, I want to load medium-resolution roses images.


If I included all these images within the game then my game size increased too much so I have decided to download these images when the game first time started. Then after I don't require to download or load them from the webserver.

But honestly, I don't know how to achieve this so please give me some starting point for this.