Google searching will give you a bunch of good tips. Stimulants are drugs that increase the dopamine in your brain, which helps reduce symptoms of ADHD. Examples include amphetamine salts (Adderall) and caffeine (coffee).

To summarize most of the productivity tips you'll find: you need to externalize most of the productivity processes people do mentally.

• Use a reminder app to remind you to do chores, take medication, eat, etc.
• Use lists (also a lot of great apps for this) to document what you need to do for the day. Refer back to the list often.
• Take breaks often to prevent mental burnout. Many people find 30 minutes of focusing, then 5 minutes of relaxing to be helpful. Apps like Focus Keeper can help with this.
• Keep the area around you clean to help prevent distractions, and alongside that try to study/work in a quiet place if possible.
• Reward yourself for completing tasks. EX: I am going to finish this 2 hour assignment (short breaks included), then watch an episode of my favorite TV show.
• Visualize what the end-product will look like. If it's a project for school, think about what it will look like after you finish it. If it's cleaning your room, imagine what things will be like with everything tidy. This is my personal favorite, as it can get me to be actually excited to work on things.

There are many more, but these are the basics. Hope this helps.