When you hover over any standard, that standard will expand, and a copy button will appear. Click the copy button for that individual standard. Then, hover over the standards card to which you want to copy the standard, and then click the paste button at the top of that standards card.
To copy ALL of the standards from a lesson plan, you'll see a copy and paste button at the bottom of every standards card. Click the copy button on one standards card, and then click the paste button on another standards card to get all of the standards from one lesson to another.
To summarize, click the copy button next to the standard to copy a standard. Click the copy button at the top of the standards card to copy all of the cards on a lesson.