It sounds like you are adding a LTI 1.1 tool to Canvas and if so the form in Canvas doesn't allow you to control which placements are enabled for the tool. If you want to set this up the easiest thing is to use this tool to create an XML file: https://www.edu-apps.org/build_xml.html
This allows you to more easily configure the placements (called "Extensions" in the tool). Then add the tool to Canvas using the XML and it should appear where you expect.
With LTI 1.3 (added as a LTI Developer Key) the UI allows you to select the placements you want to enable although there are still some features that are only available by supplying a config file.