If you already have a account:
It is considered one of the most stable releases, holding the record for the longest time as the "latest" version (303 days) before 1.13 arrived.
By following these steps, you should be able to download Minecraft 1.12.2 Java Edition. Enjoy your Minecraft experience!
How to Download Minecraft 1.12.2 (Java Edition) version 1.12.2, known as the World of Color Update