Question: What is the significance of this Thangka in the picture? What does the scripture in it mean? What should I pay attention to when placing? thank you

This is not Thangka, but a mantra wheel in Tibetan. I don't know Tibetan, and I don't know the specific content, but what is certain is that mantra wheels generally bless believers. So:

First of all, worship it like a Buddha statue and hang it on the wall, but don't put it in the toilet, bedroom or noisy place. Flowers, water and so on can be provided below. Where there is a mantra wheel, it is like the presence of Buddha, so it should be treated with respect.

Secondly, following the teachings of Buddhism and cultivating jackfruit of six degrees is bound to be a great achievement.