You most likely have a website and would like to grow your subscriber base so your newsletter reaches more people. Aside from the option of allowing public subscriptions you also have the option of using a form with the specific purpose of subscribing your readers.
This form can be used on your website, portal, school app or any other place you can insert hyperlinks.
Getting the form URL
Each publication has its own unique form URL, so you'll need to make sure you use the correct URL to ensure subscribers get put into the correct publication.
On the Dashboard for your publication, from the left menu select Email Subscribers
In the top right corner, click the Options menu and choose Get Subscribe Form URL
In the popup window that appears, you can copy the URL
Go to your website, portal, school app or wherever you want to put this form and insert a hyperlink to this URL
Now when your community clicks that link they'll be taken to the form where they can subscribe to the newsletter. You can try it yourself - just paste the link into your address bar in your web browser and you'll see exactly what your readers will see.