help

what tools do and where they are
https://helpx.adobe.com/photoshop/using/tools.html

missing tools
https://helpx.adobe.com/photoshop/kb/bringing-back-tools.html

if you don't see tools or layers
http://stevecampbellhillwood.blogspot.com/2015/12/if-you-dont-see-tools-layers-etc.html

opening photos
http://stevecampbellhillwood.blogspot.com/2015/12/find-place-hi-res-photos-in-photoshop.html

copying and pasting a photo into a Photoshop document
http://stevecampbellhillwood.blogspot.com/2016/09/pasting-photo-into-photoshop-document.html

resizing photos
http://stevecampbellhillwood.blogspot.com/2015/12/resizing-photo.html

zooming in
Go to Window>Navigator

erasing
magic eraser for large areas of the same color
http://stevecampbellhillwood.blogspot.com/2015/12/photoshop-tools-explained.html

erasing smaller areas
http://stevecampbellhillwood.blogspot.com/2016/01/eraser-tool.html