There should be in Theme plugins. Are you sure that you installed it. Please unpack it manually in
/plugins/themes
and it will appear in Theme Plugins. Enable it, and you will see it in Appearance part where you started this forum question.
Does it work now? Please have in mind that Bootstrap theme has copies of some template files. If you need to change them you have to edit them in proper Bootstrap folders.
This is an older post that deals with a different version of OJS, can you post your question in a new forum post, please? This will help keep the forum more organized.