Playing in time matters more than any lick. This lesson uses only open strings so all your attention goes to the click.
Every exercise is in 4/4: four beats per bar. Count out loud, "1, 2, 3, 4". In the first exercise you pick once per click, with a downstroke. In the second you play two notes per click: a downstroke on the number and an upstroke in between, counted "1 and 2 and 3 and 4 and".
The third exercise mixes notes and rests. An empty column in the tab, with no number on any string, means silence: touch the string with the side of your picking hand or lay a fretting-hand finger on it so the note stops, but keep counting and keep your hand moving down and up as if you were playing.
The most common mistake is rushing. Your notes should sit on top of the click so it almost disappears. If you can hear the click clearly next to your note, you're early or late.
Start each exercise at 60 bpm. Move up 5 bpm after four loops in a row where you never lose the count.