how to i attach photos from the photo library to an email?

File>Share>Mail

Or you can grab the picture in the thumbnail view and drag it over to the email you're sending.

Or you can File>Export the picture to the desktop and drag it in from there

Share and Dragging will send a picture with keywords & location information. With Export you can remove that info.

What app do you use for email? Add it to the Share menu. Or, use the attach dialogue in the email client. Both of those are easy.