By typing RESTART=<step number in the Jobcard at the beginning of the JCL.

For instance, if the step you need to restart from is called STEP002,you would type RESTART=STEP002

Restart =JOBSTEPNAME.PROCSTEPNAME in the Job card

If you want to restart a step in cataloged proc. We have to give  

Restart =PROCSTEPNAME.JOBSTEPNAME in the Job card.

For Eg :-

A job is having 5 steps //------ job card--------

                                   //step1

                                  //step2

                                 //step3

                                 //step4

                                //step5        exec    proc= step1

                                                                        step2(abended)

sol:- RESTART=PROCSTEP.JOBSTEPNAME