If you have received cactus seeds from Blueprint Earth, here's the info you'll need to grow them!

Your seeds are the Orange Barrel Cactus, known scientifically as ferocactus cylindraceus. Native to the Mojave Desert, your seeds will thrive even if you are not a professional gardener. Here are some simple care instructions to help you succeed with your new new cacti.

SOIL: Good potting mix with plenty of drainage is important for cactus seeds. 

PLANTING: Use clean, shallow containers. Water the soil once and let it drain before you add the seeds. Put the seeds on top of the soil at least 1-2cm apart, and then add a small amount of soil on top. Do not plant your seeds too deep! A few millimeters of cover is all you need. After you've covered the seeds, put a transparent lid (plastic wrap works very well for this) on top of your container. This will retain moisture and allow light inside.
GERMINATION: Keep your seeds away from direct sunlight, as that can be too hot. Indirect sunlight is perfect. You should not need to water your seeds again if you leave the cover in place. You should see sprouts in 3-5 weeks, but they make take longer. When you can see spines on your cacti, take their cover off during the day. Do not let your soil become dry, but do not drown your cacti either! 
REPOTTING: Your cacti will be ready for new pots when they are the size of marbles (~1 cm diameter). Choose a new pot that is no bigger than twice the diameter of your cacti. Make sure you wear gloves!

Enjoy your new cacti!