Click on "Upload" on the Home page or the PhotoStream page.
Choose photos by dragging and dropping or by clicking on the webpage
and choosing from the dialog box.
Click "Upload X photos" in the upper right hand corner
Click "Upload to Photostream" in the dialog box that appears.
Your photos will now appear on
the home page.
assign them to an album, mouseover "You", and select "Albums".
Click on the "Add New Album" tile
Drag your photos from the strip
at the bottom of the page (holding shift allows you to select the first and last picture in a series; holding control allows
you to multiple select individual pictures.
Replace "new album' with an appropriate name. It will be useful if you append your name to the album.
This takes you to the "Albums & Collections"
page, where you can see other albums and collections. If there are other albums covering the same event, you can add
them to an existing collection by dragging them onto the appropriate collection in the left panel. You can also create
a new collection by clicking on "Create a new: collection" above the left panel.