On most Linux distros it is possible to generate the htpasswd file entries simply using the htpasswd command line util.
On FreeBSD the easiest way to accomplish the same task is using OpenSSL itself
openssl passwd -apr1 >> /path/to/htpasswd.file
Enter the password twice and the hash will be printed into the file
Then open the file and add the username followed with a : before the hash
It will look like