Open a File with Illustrator
To open a file with Illustrator and Photoshop is easy as can be. The tricky part is deciding what program to use with which file type. Between the two you can open 100's of file extensions, but the most common for Illustrator is .AI, .PDF, .EPS, and .SVG. Illustrator is mainly a vector based program.
Once Illustrator is open, click File < Open, and navigate to your file and hit Open.
Once your file is open, hit Alt + 0 on PC or ⌘ + 0 on Mac to bring the artwork to front and center.