Can not use r=site/login

I can not go to index.php?r=site/login, help me please link login admin, thank you!

error show:

Seems that U are missing ‘assets’ folder

make sure the "assets" directory exists and its writable (has write permissions)

If i don’t remember password login via host.

I can not login admincp??

where link login admin control exceptr=site/login??

thank you