buddypress help

i ave a mutlisite network, i install buddypress but i dont want it activated on the main site

i would want it install on a sub website example zvabiztalk.com/community

but if i should activate the plugin from that zvabiztalk.com/community admin it sayin i dont have permission to buddypress install wizard

but i dont want it activated on my main domain
how can i fix it?