You can try some well-known comic reading platforms like Comixology or Marvel Unlimited. They might have a collection of Flash comics available for online reading.
You could search on sites like Marvel Unlimited or DC Comics official website. But keep in mind that not all of them might be free and the availability might vary depending on licensing and region.
Well, the origin of Flash varies depending on the comic version. Sometimes it's a lab experiment gone wrong, and other times it's a mysterious force that grants him super-speed. But in most cases, it's a sudden and unexpected event that transforms him.
The Flash isn't usually depicted as Hispanic in the mainstream comic versions. However, there might be alternate universes or specific story arcs where his ethnicity is presented differently.