Seeds: there are two types. One self pollinates, one needs another variety to pollinate it. Read about the variety you choose to grow. Google it. All watermelons are not the same. In general, they are started on mounds because the soil is warmer on a mound. If you start indoors, they need a heat mat under them or can take a long time to germinate. Water thoroughly and plenty - they need a lot! Towards end of season, pinch off any new melon babies (you can pickle them, cook in soup or slice into salad) so they don’t suck energy from the ones that will have time to ripen. They can take a lot of space but can be pruned back; there are various techniques.
We plant watermelons out in the old pasture/field areas. We have a rototiller for our tractor and have a narrow and long area that we plant wildlife plots. The watermelon can take up as much space as they need out there; however, they are not protected and the deer tend to sample them just before they are ready to be picked. We do have a problem with weeds out there, it is hard to weed with the vines spread out. This year we are going to mulch around the plants and see if that helps with the weed issue.