I think we need to clarify something:
You don't "open" images in InDesign -- you "place" (some people call it importing) them into documents. InDesign natively supports placing Adobe Illustrator and Photoshop documents -- but it doesn't OPEN them -- instead it links to them. Once we're done, make sure you inspect/play with the Links panel (Window>Links) to get a better idea about what InDesign (typically) does with images.
Try this (Since you're a Mac user, I'll use Mac keyboard shortcuts)
Press <Command-N> (to create a new document ... menu path is: File>New>Document)
For the time-being, create a standard Letter size (you can change the document size later if you want) and press <Command-D> to open the Place window. Pick your Photoshop file (if you want a LOT of control on how it's imported, make sure "Show Import Options" is checked) and click OPEN.
Your cursor will be loaded with the image -- click anywhere you want to place the image in the document.
You cannot edit a Photoshop file in InDesign -- for that, you'd need Photoshop. There is no such plug-in for the term "open" that you're asking.
Wanting a more detailed answer? Here's Adobe's view on Placing (importing) graphics [warning, I'm about to share way-more information than you actually needed -- but if you want to learn... read on]:
The Place command is the primary method used to import graphics into InDesign because it provides the highest level of support for resolution, file formats, multipage PDFs, and color. If you’re creating a document in which those characteristics aren’t critical, you can copy and paste to import your graphic into InDesign. Pasting, however, embeds a graphic in a document; the link to the original graphic file is broken, and you can’t update the graphic from the original file.
The options available to you when you place a graphics file depend on the type of graphic. These options appear when you select Show Import Options in the Place dialog box. If you don’t select Show Import Options, InDesign applies the default settings or the last settings used in placing a graphics file of that type.
The names of graphics you’ve placed (imported) appear in the Links panel. Note: If you place or drag a graphic from a removable media, such as a CD‑ROM, the link will break when you remove that media from your system.
For a video on importing content into InDesign, see
1. Do one of the following:
• To import a graphic without first creating a frame, make sure that nothing in the document is selected.
• To import a graphic into an existing frame, select the frame. If the new image is larger than the frame, you can refit the frame later by choosing Object > Fitting > [fitting command].
• To replace an existing image, select its graphics frame.
2. Choose File > Place and select one or more graphics files of any available format. If you select multiple files, you can click or drag in the document to place the selected files one at a time.
3. To replace an object you selected, select Replace Selected Item.
4. To set format-specific import options, do one of the following:
• Select Show Import Options, and then click Open.
• Hold down Shift as you click Open or Shift-double-click a file name. Note: When you place a graphic created in Illustrator 9.0 or later by using the Show Import Options dialog box, the options are identical to those for PDFs. When you place an Illustrator 5.5–8.x graphic, the options are identical to those for EPS files.
5. If the Place dialog box appears (because you chose to set format-specific import options), select import options and click OK.
6. Do one of the following:
• To import into a new frame, click the loaded graphics icon in the layout at the place where you want the upper left corner of the graphic to appear.
• To import into an existing, unselected frame, click the loaded graphics icon anywhere in that frame.
• To import into an existing selected frame, you don’t need to do anything. The image automatically appears in that frame.
• To replace an existing graphic, hold down Alt (Windows) or Option (Mac OS) and click the loaded graphics icon on the graphic you want to replace.
• To place all the specified pages of a multipage PDF at the same time, one overlapping another, hold down Alt (Windows) or Option (Mac OS) and click the loaded graphics icon where you want the pages to appear.