The theme is your site's clothing: the same content can look professional or amateur depending on it. Installing is easy — what matters is what you do around it.
First: a backup
If the site is new and empty — experiment freely. If it is live with content: backup first. Changing a theme can displace widgets, menus and content built with another builder.
Way 1: from the official catalogue (safest)
Appearance → Themes → Add new → search (e.g. Astra, Kadence, GeneratePress, Blocksy) → Install → Activate. These are reviewed, maintained and free in their base version.
Way 2: from a ZIP (a purchased theme)
If you bought a theme you get a ZIP: Appearance → Themes → Add new → Upload theme → choose the ZIP → Install.
Careful: some packages contain many files; you need the ZIP with the theme itself (usually the installable WordPress file), not the whole bundle with documentation.
Way 3: via FTP or File Manager
When the ZIP is too big to upload through admin: unpack locally and upload the folder into wp-content/themes/. Then Appearance → Themes → Activate.
Right after activation — 5 things
- Open the site and check: menu, logo, homepage, one article, the contact form
- Check on mobile — that is where most themes fall apart
- Appearance → Menus: the new theme has its own positions; the menu usually needs reassigning
- Widgets — the same applies
- Test speed (PageSpeed) — if the theme brought 2MB of code, you will feel it
If the theme demands plugins
Many purchased themes want a set of recommended plugins. Install ONLY the required ones — every plugin is weight and risk.
Our usual advice
A light theme (Astra/Kadence/GeneratePress) plus Gutenberg = a fast site that is easy to maintain. A heavy all-in-one template with 50 demos looks tempting, and two years later it is a burden nobody wants to touch.