Make sure you use potting soil! Do not use garden soil. What is this automatic watering gig with this planter? Put this planter in the sun for starters. Use good ole OSMOCOTE 14-14-14 one time at the beginning mixed into your soil. Less is better. I don't like starting seeds in such a large POT. It would be far better to purchase some of those little peat pots to start your plants. You will also be able to know what has germinated and what has not. Once you've got plants that have roots going out through the bottom it is time to plant in your planter.
I would try a huge batch of peas for the spring. These you won't have to start in tiny pots. Peas love the cold nights of spring and you won't go wrong. Press your potting soil down to get rid of air pockets. Place seeds on top 3 inches from each other. Forget rows. Push the seeds gently into the soil at least an inch to 1 1/2". You'll have to add a support once they get going.
Water by hand. Now is not the time to mess with automation anything. Water ONLY when dry at least one inch from the surface once your plants have 2 to 3 sets of leaves. Otherwise keep the surface moist while peas are babies. Try to not use tap water. Bottled water is far better. Peas are very forgiving.
The next batch of vegetables should be a SALAD BOWL. Mix all kinds of lettuce, spinach, radishes, carrots and after firming NEW SOIL and sprinkle over the top. Not too thickly. Cover with a 1/4 " of soil from your bag and again firm soil and seed. A couple of seeds per square inch. The radishes will mature first and you can pull them to eat and cause more room for the lettuce. As soon as the lettuce has baby leaves start gobbling them up. Choose a few lettuces to allow to mature. Pull the lettuce roots and all to allow room for a few mature heads. The carrots will mature last. While plants are tiny, use a spray bottle to moisten the soil, do not soak the entire pot of soil.
I'd get a few of these planters or go and get pots. Use STARTS from the store or try germinating your own; broccoli, cabbage, tomatoes. For a planter this size use only 2 tomato plants. Seriously. Using just pots with drain holes is plenty to grow all kinds of stuff. I've grown cucumbers, 4 starts per 10 gallon pot for instance. They all need sun all day to produce edibles in any quantity.
Make sure you use POTTING SOIL. Do not bother with making your own or using your garden soil! That Osmocote fertilizer will be all that is necessary, follow the directions to the letter! You should only use once for the season. Automatic watering is only for experts do not try to use that. Make sure your pot drains well...do not put any rock or gravel beneath the soil. Put a tray beneath to protect your deck and don't allow water to sit in the tray at the bottom beneath the drain hole where the pot is in contact with the water.
This is a great way to begin gardening. Don't expect total success and do keep asking questions. Every question you ask that we can answer will help you to not have to learn by mistakes...like the rest of us have already done!