Under each activity, you'll see a lined icon on the left. Click on this to access the screen where you can add achievement standards.
Get started by clicking on Add Achievement Standards. This will bring up a list of standards and a drop-down menu for choosing specific year levels.
Choose your year level and check off the standards you want to include. If you change your mind about it, just uncheck it.
When you are finished, simply click the back arrow in the top left-hand corner of the screen. You will now see your added standards appearing beside the activity. You can add more again if you want to by re-clicking Add Achievement Standards.