There are thousands of algebra books out there that break down algebra to its easiest components. Many learning styles in these books are different so take the time to go through them and find one that looks like you might understand or one that accommodates your learning style. Many books explain some algebra concepts better than other. Choose a variety of books or online courses. You can get a live tutor. It will be much easier to learn from someone who s already familiar with the concepts of algebra. There are online communities where people discuss their algebra problems and help each other. Remember though that even if you are a member of one the many popular interactive algebra communities you still need to study and practice a lot.
Get some addition practice while reading picture books together. There are a ton of great picture books that have overt and hidden addition facts and practice, but you can turn any book into a lesson in addition. If you read a page with a picture of a forest, you might say to your child, "I see three trees and four flowers. How many plants are there all together?" You can add characters, shapes, items, or anything in multiples.