Editing stock image.

Are you editing text in the downloaded file?

If not you don't need to open it, just place it in a new doc and type what you want in that new doc.

I have recorded a series of videos on editing stock images: Check out if they help you.

https://www.youtube.com/playlist?list=PLVqhHu3CSohVhofyDlCIh3Z-Qk8qSmMqZ

For a better understanding of what you're seeing:

The bounding box of a selected object is the color that's assigned to the layer on which it resides. The default color of Layer 1 is indeed blue, but when a second layer, Layer 2, comes into existence, its default color is red, so your image is just likely on Layer 2, and that's why its bounding box is red.

So you're aware, if your "image" is a raster image—made of of pixels as opposed to vector elements—you won't be able to "edit" it, per se. That is, Illustrator is not a a raster image editor; it is a vector graphic application. You can place or paste a raster image within the Illustrator editing space, but it will behave as a static object, and you won't be able to change anything within its pixel makeup. You will, however, be able to add text to the composition as a separate, vector object using the Type tool, if that's your objective.

The object outline in red can be on a different layer, click on an empty area, using the selectio tool (the fist tool, shortcut v) to unselect eveything, then select the txt tool, shorcut T, and click totype on thr image. 
With the text still selected you can change the typeface, size, ...