Age consent pop up

Hello everyone. I’m a super n00b but doing my best to learn new things.

Question: How do I create an age consent pop up window when someone enters my website? It could basically be “I’m over 25 years of age” which allows you to enter. And one “I’m under 25 years of age” which links you to something else. The background of the site should be blurred or somehow preventing people from seeing what is behind the pop up.

Thanks guys! Please remember that I’m a n00b so super eternally thankful for pedagogical comments (Explain Like I’m 5) and not “try the x tool”. <3