Certified GKH Gardening Expert
There are many ways to acidify soil. It is worth noting that while yellowing leaves can indicate soil pH being off, it can also indicate a number of other things.
You may want to test your soil beforehand. This will help you to know exactly how much of an acid that you need to add, since adding without first knowing the pH can make things worse. This article will help you to test your soil: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-soil.htm
this article will help you to acidify your soil: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/raise-acid-level-soil.htm
This article will help you to compost so that you can increase soil fertility and vigor, naturally: https://www.gardeningknowhow.com/composting/basics/ultimate-beginners-guide-composting.htm