A prototype turns separate screens into something a person can actually try. Instead of describing a flow, you let someone tap through it: open a page, choose an option, move to the next screen, and see what happens. That simple change reveals problems that static mockups hide, such as a missing step, a confusing button, or a dead end.
Start by choosing one task to test. A good task is specific, for example signing up for a newsletter or booking a visit. One task keeps the prototype small and focused. List only the screens that task needs, in order. A prototype need not cover the whole product to be useful.
Link the screens into a flow
Connect each screen with the action a user would take. A button should go to the screen it promises, a back control should return to the previous step, and a form should show what happens after sending, even if only a simple confirmation. Check every link by tapping through slowly, as if you had never seen it.
Keep the prototype honest. Use realistic headings and labels, not perfect imagery or final copy. Testers should react to the flow, not admire visuals. Leave out screens outside the task, rather than linking to a half-finished page. The planning behind this step is covered in Wireframing a Website in a Day, which shows how to settle structure before adding interaction.
Decide what to watch for
Before you invite anyone to test, write down what you want to learn. Useful questions include: can people complete the task without help, where do they hesitate, and what do they expect to happen after each tap? Decide in advance what counts as success for the task, so you are not tempted to move the goalposts after watching the first session.
Also prepare a short, neutral introduction: you are testing the design, not them, and there are no wrong answers. Ask them to think aloud, saying what they seek and expect next. Their words often matter more than finishing, because they reveal the thinking behind each tap. For colour and readability inside those screens, Designing Accessible Color Contrast Step by Step is a useful companion read.
Run a short, calm test
A short test is enough. Sit with one tester at a time, give the task in plain language, then stay quiet unless they are truly stuck. Note pauses, first taps, and moments of doubt. Do not argue with feedback in the session. Afterwards, group notes into patterns: problems seen for more than one person top the fix list.
Finally, change one thing at a time and test again if you can. A prototype is a tool for learning quickly, not a presentation to defend. Keeping it tidy as it grows matters too, as explained in Organising Figma Files So a Team Can Find Anything.