Similarly to adding almost anything to your site, to add a gallery, you use the add element again. Each gallery you will see will be different from each other. From professional looking galleries to the less so professional. Wherever you choose to place a gallery on your site, always make sure the images are appropriate for the page or your website.
A perfect example would be a photographers portfolio website. They may have different pages for different types of photos such as nature, cars even maybe something small such as street signs. Having a car page would mean, no images of nature should be in the gallery of the car page, unless the photo over laps each category. Then the photo could be an exception.
On WIX there is a wonderful SEO tool called SEO Wiz. It makes the basic steps of SEO even easier by offering you suggestions, such as keywords which relate to your website. Once you set your keywords the tool allows you to analyze the keywords. Have a mixture of short-tail and long-tail keywords, as long-tail keywords are easier to rank for. The tool then offers you an SEO plan, which will hopefully start to rank your website.
With WIX, you also get a free domain. The main problem with this domain is that ‘WIX’ will be attached to the address. This is bad for search results and your website, if you want it to be successful. Therefore you would want to buy your own domain an connect it to your website. Names can be expensive, especially premium names. This would involve country codes such as ‘.co.uk’ and ‘.ie’ a lot as well as short-tail keywords such as cars or amazing cars.