as i am new to salesforce could you guide me on following.
when the opportunity stage changes, task should create using process builder.
i did with entry criteria is opportunity.stagename ischanges is true then create new record whith required fileds.
but task is not creating for the opportunity.
Anybody can you help me in this.thanks
Like @Dan pointed out, it sounds like the Process isn't being triggered. If you are using the RecordTypeId in the criteria, make sure you are using the CASESAFEID or the 18 char Id in the criteria.
You could also try using starts with vs equal while using the 15 char Id.
To relate a task to a lead you have to use the WhoId (more info here: https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_erd_activities.htm ).
In the process builder you have to map the field "Name ID" not the "Related To ID".
Best Answer
You need to add following in Set Field Values section,
then only task will be getting created under Opportunity.