Where is the fastutil-8.3.1.jar file supposed to be placed

I keep getting the 

couldn't resolve all artifacts for configuration error, i think its because of gradle server being bad, instead of trying again later, i thought why not install the file bellow manually:

Https://maven.minecraftforge.net/it/unimi/dsi/fastutil/8.3.1/fastutil-8.3.1.jar

So my question is: where should i put the file after downloading it manually?