can't insert photos onto pages document

Make sure your photos are in JPEG format.

Simply drag and drop the selected photograph into your Pages Document.

Resize etc using the handles surrounding the photo.

Click format: Style: Image: Arrange and adjust to your requirements.

Are you using Pages '09, or Pages v5.5.3 on Yosemite?

In Pages v5.5.3, you click the media toolbar icon, and providing you had updated to iPhoto version 9.6.1, you will have media entries for iPhoto, and the new Photos libraries (if you launched Photos once before using Pages). Simply click an image and it is deposited into Pages. You can also drag and drop several image formats from a Finder window location directly into Pages v5.5.3.

Some of those Pages v5.5.3 acceptable image formats are: png, jpg, gif, pdf, eps, tiff, psd (Photoshop), jp2 (JPEG 2000), bmp (Microsoft bitmap), and others (but not svg).

Pages '09 v4.3 can only see the iPhoto library from the media toolbar icon — again providing iPhoto is the above version. A double-click on an image does not deposit it into Pages '09 — instead you need to click on the image and then drag/drop it into the document. Drag and drop of images from the Finder window is also supported here.

Both applications provide a Insert ▸ Choose… menu item for inserting images too.