You have bought weed seeds. Then the next step is to have them germinate. For this purpose use something that retains moisture well, for example cotton wool, napkins or a handkerchief. Wet these and place the seeds inside. It is not necessary the cotton wool/cloth is soaking wet, properly humid is enough. Place the cotton wool/cloth in a small bowl and cover it with some foil so that it remains humid. Prod some small holes in the foil so that oxygen does reach the weed seeds.
Check the bowl on a regular basis if it is still humid enough and if the weed seeds already start to burst. It takes 1 to 5 days before the weed seeds start to show a small white root. When the root has a length of 3 to 5 mm, it is ready to be potted.
You can obviously also cover the weed seeds with soil without germinating them first. This is of course the way it happens in nature, however the chance a weed seed really flowers is smaller.
An 80% to 95% will germinate, depending on the quality of the weed seeds.