You can find the metatag description in the page properties of the respective page under the metadata tab. Use the description for a short summary of the content of the page. Try to include the most important keywords (search terms) for your page. If it fits, add a short call to action such as click here or read more.
At the moment, two-line descriptions are displayed on Google again, which means they should be no longer than 156 characters. If you have several similar pages, use a specific description for each to avoid duplicate content. Duplication of content decreases our search engine ranking! You are also welcome to use special characters → as these can contribute to better readability. √
You can use snippet generators to help you with this, such as this snippet generator from Sistrix.