Raspberry pi 3 b+ operating system will not boot

Hello, I installed your operating system on a 32 g sd card. Then I inserted the sd card in my Raspberry pi 3 b+ but the operating system does not start. The red LED turns on instead the green LED remains off.
A little help would be helpful, thank you in advance.

Hello, I solved.
I had committed a small error: I had not installed, in truth, the operating system in sd card. Errare humanum est.
A greeting from Italy.

Sounds good, thanks!