The creation of a Dialog in process using Dynamics 365.
Step 1: Open the Dynamic 365.
Step 2: Navigate to Sales –> Settings –> Process Center –> Process
Step 3: Click On Process and you will the same screen as below image.
Step 4: Click on New Button to create the new process.
1. Provide the name of the process, in this example “DIalogFirst” is the name of the Process.
2. Select the Category as Dialog.
3. Select Any 0ne Primary Entity. Click Ok.
Step 5: A Pop Window is opened, make sure that process must run on “on demand process”.
Step 6: Right Click on the steps and click on add steps, In that select Page.
Step 7: provide a Unique Name in the Description, for example it is named as “Page1”.
Step 8: Click On the page row and click on Add step, select “Prompt and Response” as below.
Step 9: After Selecting the Prompt and Response, Enter the Description in description bar and click on set properties.
Step 10: Enter the prompt details like prompt text and tip, moving on to response details, select Response type as single line text, data type as text and select radio button Yes for Log Response. Default value is left blank.
Step 11: Click on Save and Close.
Repeat the steps from 8-11 by creating prompt and responses.
Step 12: How to Work With an Option set, creating the prompt by preferences.
1. Select the response type as Option set(pick list).
2. Response type as Integer.
3. Log Response as Yes by checking the Radio button.
4. Add the items providing with values to the option set.
Step 13: Click on Save and Close button.
Now Update the Record, select the page and click on “Add Step”, select the “Update Record”.
Step 14: You can see the step just below the page.
Step 15: Click on Set Properties, of update record as follows.
You can see the following image 
Step 16: Based on prompt and response, mouse focus should be placed on the fields.
Go to look for and pick the prompts created, click on “Add” and click “OK”.
Step 17: Select the option set from local values and place the focus into the field but do not select any option set. Click on Add and Ok.
Step 18: Click on Save and Close.
Step 19: To Test save and Activate the process.
Step 20: A Pop Window is opened for confirmation whether to Activate or Not?
Step 21: Go to Advanced find and, and select the “Lead” as entity and search for the records.
Step 22: Open the record, and click on the extension and click on the “Start Dialog”.
A new pop-up window is opened and asks to select the dialog to run, select the Dialog and Click on Add Button.
Step 23: Finally You can see a new window is opened with prompt and response, and enter the details and click next and finish.
Click on Finish Button.
Step 24: Refresh the record to update the values.
Finally the Updated Values can be seen here.
This is how the Dialog process works.