How to install/use:

Your saves are located in C:\Documents\BioWare\Dragon Age The Veilguard\save games\

Extract the zip into that folder. (In some cases, the zip file will make an "extra" folder, so when you extract it, it will be a folder too deep. Easily fixed by extracting into your downloads folder, then click into the folder that pops out, and move the folder inside the first folder into the numbered save games folder).

To use mods, you will need to install Frosty Mod Manager. This guide by PinkyDude explains in great detail on how to use them and install it. There's links to the mod manager in this guide too.