Honestly gardeners world is pretty great for getting into things. If you don't want to watch the programme then take a look at their monthly magazine.
Suggest you create some proper flower beds in your garden as a starting point. Good idea to get a water butt too (often subsidised by your water company).
Work out what sort of soil you have (surprisingly easy to do).
Watch and note how the weather affects your garden- where gets the sun and at what point of the day? Any hot spots, shady spots, dry spots, wet spots?
That's pretty much all you need to know to choose some plants for your new beds. Go along to a garden centre once a month and choose a plant, it's a good way of making sure you have something in your garden for every season.
Trial and error - everyone makes mistakes as they go along, so don't worry about. You'll learn as you go.
Give everything a good soak when planting it - and trees especially need regular watering to help them establish in the first year.
Finally, for maximum enjoyment of your garden, once you've worked out the above, go and have a wander and sit in different places in your garden. When you find good spots of chilling out and enjoying the view, make sure you keep a space there for a seat or a patch of grass to lie back on. You'll end up loving your garden all the more.