How to reduce the file size of jpg?

Right, there are a couple of simple ways to sort this. The main way is by changing the compression or 'quality'. When you save the file, you can often see a slider from 1 to 100. The lower the number, the smaller the file will be. Just don't go too low, or the picture will start to look a bit blocky and naff.

You can also just make the picture smaller. I mean changing the dimensions, like its width and height. If it’s just for a website, it doesn’t need to be massive. There are loads of free websites for this. Or you can use software you've already got, like Paint or the Photos app. Just look for a 'resize' or 'export' option. It's all about finding a good balance.