Copying from Wikipedia to this site is perfectly permissible because both use the same license. That license is designed to encourage such use. It saves much duplication of volunteer resources.
Attribution
However, we must include the proper attribution so that readers can refer to the original and discover its authors. It is easy: whenever you do such copying from a page in the English-language ("en.") version of Wikipedia, just add the following template near the bottom of the page: "Wikipedia|" inside double curly braces, i.e. {{Wikipedia|}}, then before the final braces type or paste the name of the Wikipedia article.
You need to add similar attribution for material copied from other languages of Wikipedia and other CC-BY-SA projects. See http://familypedia.wikia.com/wiki/Template:EsWP for an example of such a template (for Spanish) in another Fandom site.
Content
Note that Fandom wikis are not intended to duplicate substantial portions of other sites without adaptation. You may copy all or part of an article (best to copy the whole page from its "Edit" box so that categories, footnotes, links and templates are preserved) to start off a page on the subject. Red links should be considered as starters for new articles or redirected back to Wikipedia by prefixing "Wikipedia:" straight after the opening brackets.
However, you or another contributor should then adapt the article so as to reflect this particular site's emphasis. Wikipedia has standards of "notability"; this site has no such restriction, which means that a Wikipedia article copied here may then have much material added to it that would not be wanted at Wikipedia. Conversely, some of what is in a Wikipedia article may be of no value here and can be trimmed.