You can remove the "Powered by Shopify" link from your footer by editing the theme code. From your Shopify admin, navigate to Online Store > Themes, click the … icon beside your theme, and choose Edit code.
Impulse
In the Sections folder, open the footer.liquid file and delete this line:
<p class="footer__small-text">{{ powered_by_link }}</p>Motion / Streamline
In the Sections folder, open the footer.liquid file and remove the line shown below:
<span class="footer__powered_by">{{ powered_by_link }}</span>Expanse / Fetch / Gem
In the Sections folder, open the footer.liquid file and delete this code:
{{ powered_by_link }}If you’re using Expanse 5.0.0, Fetch 2.0.0, or Gem 2.0.0 and newer, look for the code in the section-footer.liquid or section.footer.liquid template.
Password page
As for the password page, the "This shop will be powered by Shopify" can be removed in the password.liquid file in the Layout folder.
For Impulse, Motion, and Streamline, search for and delete the following code:
{{ 'general.password_page.powered_by_shopify_html' | t: shopify: shopify }}For Expanse, Gem, and Fetch, you'll be looking for this line of code:
{{ 'info.will_be_powered_by_html' | t: shopify: shopify }}