We're going to start with an unbelievably simple exercise. Please don't get bored and run off - it gets challenging really soon. In this exercise, you will be plucking the 3rd (from the ground) string of your ukulele with your thumb. That's all. Pluck it over and over and over. You are also going to get an introduction to tablature or "tabs", which is a system of writing music that is common when you are doing special things with individual strings. Here is a 'tab' of this exercise:
Always use a downward stroke when plucking a string with your thumb.
The letter "T" across the top signify that the note is played with the Thumb of your picking (strumming) hand. The four horizontal lines represent the strings on your ukulele. The dots represent notes - the number "0" inside each dot means that the string is to be played at the 'zeroth' fret, or 'open' position. For now, you should just think about your picking hand - later, you will see numbers inside these dots. For now, just leave your non-picking hand away from the strings, and think about that thumb.
You can click on the "play" button to hear the drill played through once, so you can be certain that you understand. Unlike our earlier lessons, we're not going to start doing this at speed (with a backing track) just yet - for one thing, it would be boring, and for another, you have enough to think about for a little while. Keep your attention focussed on the picking - get really comfortable with it - pluck that string with your thumb over and over until it feels 'easy'.