Glad I could help you get set up with OptiFine 1.19.1! It makes a massive difference for performance and shaders in Minecraft.
Simply download, run the JAR file with Java, and click "Install". Make sure your Minecraft launcher is closed first. Thanks for downloading Optifine 1.19.1
If you are looking to get the best performance, here are some key takeaways from the community: Glad I could help you get set up with OptiFine 1
To use it with Forge, just drop the downloaded file into your /mods folder. Make sure your Minecraft launcher is closed first
You might need to click "Preview Versions" on the official OptiFine download page to find the 1.19.1 release.
If you're looking for even higher performance (FPS) on 1.19.1, consider looking into Fabric with Sodium and Lithium. If you run into issues, let me know: Are you using Forge or a vanilla installation ? Did you get a Java error ? I can provide the specific steps to fix it. How to Download & Install Optifine in Minecraft 1.19.1