Error creating standby (RAC) with primary (single instance) No OMF destination specified, unable to

Hi gurus, someone knows also about this error?

I have a dataguard (single instance to single instance) and I would like to transform standby to rac:

I have Grid Insfrastructure on standby database machine

on primary database:

create tablespace UNDOTBS2 DATAFILE ...

SQL> ALTER DATABASE ADD LOGFILE THREAD 2 GROUP 21
   ('/oracle/orapro_mplex_01_EDREAL4/EDREAL4/rdo/EDREAL4_redo_21b.rdo','/oracle/orapro_mplex_02_EDREAL4/EDREAL4/rdo/EDREAL4_redo_21a.rdo')
  size 524288000 reuse;

Database altered.

.

.

Error reported on standby and recovery stoped!!!

Alter Database Enable Public Thread 2; -> this instruction goes ok on primary, but standby recovery is stopped.

on alert log of standby:-----------------------------------------------------