Adding RowLock to Insert queries


I am asked to add RowLock to the insert queries of camunda.ACT_HI_ACTINST AND camunda.ACT_RU_VARIABLE tables as these two tables are causing locking and blocking in prod db. How to add RowLock to these insert statements or is there a way to avoid the lockings and blockings and improve the performance. Could anyone guide me with this.