Open the desired photo in Photo Shop

Go to Image >Image Size

Arrow showing a huge file size of 56.1 Mb 

 longest side = 3836 pixels

Change Resolution to 72

Change longest Side (Width) to 600 pixels.

Having the Contrain Proportions boxed checked will allow the photo to resize evenly

To Save a resized copy

Go to File>Save As

Click on the desired folder to Save in

Choose Format: JPEG

Check off Save: As a copy

Click on: Save

Move the file size slider to 7 or 8

Your file size will appear under Size

Click on OK

This box will pop up when you close your original photo

Suggest clicking NO and saving your original

 Photoshop Elements Save For Web Tutorial