I agree with funny person. Get a design book from the library or Google/ Pinterest small garden design .
You can spend many nights on Pinterest making up boards of gardens you like . Search for any aspect you like - paths, water features , seating. After a while you will work out what style appeals to you and what layout would work in your space .
Learn about easy care plants. You want lots of shrubs , preferably 1/3 evergreen . Flowering one and those with interesting foliage . They will need pruned but not for a year or so , so you have time to learn what to do .
Remember that leaves will be on show for at least 7 months of the year and flowers for perhaps only a few weeks . So choose shrubs that vary in height, shape, texture and colour of foliage .
Bulbs are easy too, but it's not the time to plant them right now. Perennials are more work as they need divided every few years and some need staked .
You want plants that will have more than one season of interest, ie they will look good for more than a couple of weeks when they are flowering .
The most important thing is to plant things that like living in your garden .
The classic beginners mistake is to go to an expensive garden centre and buy things that look familiar , which is usually lavender and roses , and plonk them into the boring bits of soil around the edges. They usually look terrible and often die .
This will make you poorer and sad, and you will think that gardening is too hard . Which isn't true , it's fun and rewarding and any intelligent person who is willing to learn and do a little work can have a beautiful garden .
So, garden design. Work out what things you need and where they should go eg seating area ( in the sun ) washing line, shed, BBQ, bin storage . Do a plan stealing all the best ideas off the internet.
Make your new borders / expand the ones you have . Do any hard landscaping . Spend time and money improving the soil in your borders. This is very boring but will mean your expensive plants are more likely to thrive .
Plants - See what grows well in your neighbours gardens. If anyone has a particularly nice one, ask for their advice . Make a plant list and work out where you are going to put them . Check future sizes and conditions that the plant likes carefully online . Do not rely on the labels you will find on the plants for sale, they all say the same - plants in moist free drawing soil in sum or semi shade .
Learn what plant names mean as they give important information.
Paint or stain fence now and put up supports . After Easter, go to your local nursery with your plant list . Ask for advice .
Buy and plant climbers, a small tree or two and larger shrubs . I mean ones that will grow big,they will be small now .
Then smaller shrubs and perennials , in groups of three or more. Buy bulbs in the autumn and fill in gaps .