Hello,
Please, check the theme requirements https://www.8theme.com/documentation/xstore/theme-installation/xstore-theme-requirements/
Max upload size is set to 2 https://prnt.sc/xfycj9 But the theme is 6M size. So, you won’t be able to install theme via Dashboard if you don’t increase the Max upload size.
Contact your hosting provider to change the limit.
Regards