When reusing previously published work in your thesis—whether it is journal article(s) or a manuscript—use the Journal Template for theses & dissertations:
Why? This template has a built-in structure for providing attribution to your original publication and avoiding copyright infringement concerns. See the FAQ from Grad College for additional information about the Journal Template.
If you've published it, probably not! Most publication agreements require that you sign over copyright to your publisher. This means you can’t easily share, republish, or reuse your work in future publications.*
This counts for both full articles and portions of previously published works (e.g. figures, images, and excerpts that are longer than a typical citation).
*You can always cite your previous work—and you should cite your sources, even if your source is yourself! However, you cannot copy whole sections of a work without permission from the copyright holder.
And remember! if you published your research with co-authors, they are also copyright holders in your research! Make sure you have discussed your plan to include your article in your thesis or dissertation and gotten permission from your co-authors to do so before you submit! It's important and it's good practice from an ethical perspective, too.