To Upload a Photo in a Post or a Page
On the Dashboard menu, click Posts, and then click Add New to display the “Add New Post”page.
On the Dashboard menu, click Pages, and then click Add New to display the “Add Page” page.
On the Upload/Insert menu, click the icon for the type of file you want to upload and the “Add media files from your computer” page will appear.
Click the Select Files button.
In the dialog box, select the file you want to upload.
To select multiple files, hold down the SHIFT key (for PC users) or the COMMAND key (for Macintosh users).
You can also drag files into file upload box area.
When your file uploads, a field appears. At the bottom of the field, click the Insert into Post button.
After you are done editing and inserting file, click on publish button. Or If you were editing existing post or page, click on update button. Until you click on publish or update button, the edited article will not be visible online.
Before upload your photo to your WordPress site, make sure resize your image. Generally a photo comes from your camera will be very large. A large photo on a page makes the page speed considerably slow. You can add thumbnail, or medium size photo into the page, when someone click on the page, it can open in a new page ot pop up there, if you have a lightbox/pop up plugin.
.jpg /.jpeg /.png / .gif
Not all web hosting areas ( your hosting package should support / allow those file types ) permit these files to be uploaded. Also be aware WordPress does not allow large file uploads. Generally the standard limit is 2MB. You may change the size limit within php config file if you know editing php codes.