How to link your own js file using chrome or other webside [closed]

I need to link one more css file to not my page but i can not open it normally because table tr is to small and i dont see what is inside. Host said it’s too much work for me he will not change css. I wrote a js file changing this css for me and I need to know how to include it. I tried to do Ctrl + Shift + J and post there some js lines but i need to load fully file with a few clicks