There is a lot of wisdom of how you should position your body while meditating, check yoga and meditation resources that you trust.
You can lie down (typically on your back) you can sit on the ground, you can stand, or even walk. I think it is most important to be comfortable, for the time you have prepared to sit/lie/stand/walk. Remember you can always adjust during your meditation if feeling discomfort.
The second important thing is to take a full breath, and not feel as though it is being constrained by your posture. Feel at ease, however you are, as though you are seated in yourself.
You’re good:) now, take a few breaths, follow them feel them notice them/ find a guided meditation app/ or online offering/ focus on a candle or any other object/ sing or chant/ recite a mantra— there are so many ways— I think it’s best to explore until you find what clicks with you.