Create LDIF for new group

# vim newgroup.ldif
dn: cn=admins,ou=groups,dc=<domain>,dc=<tld>
objectClass: top
objectClass: posixGroup
gidNumber: 3000

Add LDIF to LDAP:

ldapadd -H ldaps://<FQDN> -x -W -D "<Manager DN>" -f newgroup.ldif

To add a user to a group, create LDIF:

# vim addusertogroup.ldif
dn: cn=admins,ou=Group,dc=<domain>,dc=<tld>
changetype: modify
add: memberuid
memberuid: newuser

Load LDIF in LDAP:

ldapadd -H ldaps://<FQDN> -x -W -D "<Manager DN>" -f addusertogroup.ldif