How do I create something like this?

What are you creating this for exactly  -- the web, video, print, product packaging, something else?  I ask because final output is everything.  It determines which tools and specifications you should use to create your artwork.  

Illustrator is best for math-based vector output such as logos, drawings, icons, cartoons, illustrations and other flat colored images.  Photoshop is mainly for pixel-based raster images (photography & bitmaps). 

To learn to composite in Photoshop, look on YouTube for Jesus Ramirez  -- the Photoshop Training Channel.

https://www.youtube.com/channel/UCdQ_ZkYaMe6qPoueUyPQgpQ

The first one is an illustration, so if youre an artist you would paint it. The second one is, as Derek said, a composite. It looks to me like a comp of a photo and a painting. I second the advice to look at tutorials. Here's a good one by Colin Smith (and you can find many more by googling):

Step By Step Composite 

One thing to rememeber: You have to be careful of what images you use for these things. Make sure the copyright owner doesn't mind by checking the license terms.

You'd composite the image – LinkedIn Learning has online video tutorials on creating composite images with Photoshop, you can get 30-days free access.

For example Photoshop Compositing Tips, Tricks, & Techniques and Photographing for Compositing in Photoshop by Seán Duggan