I've been looking for best practices where to put additional link "Add to homescreen". We need to implement it while the user logs in or has just logged in. I do not want to use a pop-up to make it so important for the user as we are not a "rude" website. I was wondering if this is a good practice if I put a small button under the Remember password for those who just wants to open our website a little bit faster.
If you are talking about making user add your website to their home screen directly from the login page then you can try the following designs which don't really force user to add the website to their home screen
First Variation with a catchy attractive sentence