Start simple and slow to develop good technique
The first technique we are going to look at is playing downstrokes. This is similar to what you are doing when you're strumming but the movement is much more nuanced. You still want to use the weight of your hand to play through each string for this. Playing slowly is essential for mastering this movement.
The tab shows four notes on each string. Play all with downstrokes and then do two notes per string. Practice going up and then down all strings.