Purchase Code just 1 website

I buy license in themeforest.net but in another domain i cant use theme for wordpress

Each purchase/license is for one website only. If you want to use it on multiple websites then you need to buy new licenses each time.

but i buy theme Newspapper i can use for another domain

Only 1 domain per license.

Every domain/website/project that you want to use it on requires you to buy the theme again

Envato do not offer multi-site licenses