Since this is something your users need to do every week, the default should be to stay as much as possible out of their way in what is likely a familiar process.
- It's time to replace your patch.
[ Do it now ] [ Do it later ]
Step 2 (if they choose 'do it now'):
- Patch replacement underway. Gently frangle your patch capacitor and then press the resulting fnord to pair it via bluetooth.
[Show instructions] [Fnord]
In other words, on each step that requires direct interaction with the app, show a broad overview instruction as a prompt, and include a link to expand / pop up the more detailed instructions for whatever user actions are necessary to perform that step.
(If there are steps 3, 4, etc in interacting with the app itself, you might make the "show instructions" selection 'sticky', that is if they needed help with step 2 you can safely assume they'll also want it for steps 3 and on.)
Depending on how necessary / nonintuitive those instructions are, you may wish to invert this by defaulting to making instructions visible for new users (either on a first-time-only basis, or with the typical "[x] Don't show this again" schtick). But even in this case, there's an argument to be made for not making the user make decisions about something they have no basis for deciding yet. ("Do I need instructions? I have no idea, I don't know how complicated this is going to be. If I guess no, but turn out to need them after all, will I be able to get back here? I don't know that either. Guess I better pick yes and hope they're not too terribly long.")
If there is no step 2
If this is literally just a reminder for the user that they need to physically replace the adhesive patch periodically, then the interface should present it as just that, a dismissible notification (which, if possible, would be automatically cleared when the new patch is paired, rather than requiring user action in the app):
- It's been 9 days since you replaced your patch! For proper moistness it should be replaced once a week. [Show instructions] [Done]