root@freebsd:/root # pw groupmod wheel -m test

root@freebsd:/root # cat /etc/group | grep test
wheel:*:0:root,neo,test
test:*:1002:
		

root@freebsd:/root # pw usermod test -g wheel

root@freebsd:/root # cat /etc/passwd | grep test
test:*:1002:0:test:/home/test:/bin/csh
		

或者直接修改/etc/group檔案，把相應的用戶加到wheell組就可以

wheel:*:0:root,username