Firstly, import the photos into Photos by dragging them into Photos pane. This is best done on a desktop rather than your iPhone.
Click on the photo to enlarge it in the Photos frame, then click Edit in top right corner and this will appear:

Click on Retouch and then drag the line across to open a circle. Open the circle so that it's about twice the size of the object you wish to remove. Now move the cursor to the item until the circle covers the item. Now click and the object will disappear.
It's as simple as that, but as I said, best done on a desktop or laptop/ipad rather than an iPhone.
When you are finished removing objects, click Done in the top right corner. To return the photo to your files, just drag and drop the photo from Photos back to the folder it/they came from. The file will change from .jpg to jpeg. There is no difference between the two. Jpg will be the original copy, .jpeg is the Photos corrected copy. Both files will show up in the folder they are stored in. At this point, you can delete the unwanted version from your files. To delete them from Photos, just tap the photo and a frame will appear around the photo. Tap the Delete key and a little window will drop down:
Click on Delete and it will go to the Trash bin. Photos is part of whatever OS or iOs you have on a Desktop/laptop or iPad.