Hi and welcome to the Forums.
You don't mention the source of your photos (camera or from a card or from within the Mac itself).
If camera, for example, attach it via USB, then open iPhoto, click on File and, from drop down menu, choose Import to Library. That is where they will go.
If your source is from within the Mac, eg, Downloads, open iPhoto, File, Import, and navigate to Downloads or wherever and select it. Again, the photos will go into iPhoto.
If you regularly use a camera or iPhone or similar and want iPhoto to open automatically when that device is attached—then attach the device and Go to Applications and Choose and open "Image Capture". When opened, Image Capture will list the device and offer you a choice of what you want to happen when that device is connected subsequently. One of the options is "Open iPhoto".
Hope this helps.