You can save your gallery pictures to your IOS by first bringing up the image in the gallery viewer and clicking on the share arrow icon in the upper right hand side of the screen. Then you click on the Download Image item.
This will bring up the image in the safari image viewer like below. To save it to your device, you click on the icon that looks like a box with an arrow coming out the top of it. When you hold the phone sideways, the icon on the top right side of the screen. When you hold the phone normally, the icon is in the lower right.
Once you click the box with the arrow icon, you will be presented with this menu to select the way in which you want to use the image.
Just click the save image to save it to your photos gallery on your phone.