If the two chords are together with a bar line either side it means that you should play half of the bar one chord and the other half the other chord - in 4/4 timing 2 strums of each chord.
In that one if you're playing the 8's that would mean 4 strums of each chord, if in doubt watch the video on YouTube or on the tuition website.
HTH and welcome to the forum, good luck with your learning to play guitar!