Step 3: Create a flowchart

After having written the explanation of the user journey, it's time to map it on a flowchart. You don't need to map the entire Registration/Login flow, but a small chunk that reflects your user story. It starts when users press the Like or Comment buttons and ends when they have been logged in, redirected to the page they were looking at.

Plan how users would move through screens and how their actions and other conditions can influence their user journeys. Having done that, you'll get a pretty clear idea about how many screens you need to wireframe. In this case, it's the login screen, the retry login screen, and the confirmation modal.