http://support.apple/mac/startup on my screen, what do i do

Your link is not working. Can you tell us what you saw?

Also please describe any symptoms. related or not.. We cannot see, touch, nor remotely access your computer so we need as much text description as you can provide to help in this text-based format.

The URL:

https://support.apple.com/mac/startup

…gets to this support article:

If your Mac doesn't start up all the way - Apple Support

…which has some troubleshooting information.