You need to use scissors and a compass for this, so make sure you get help if you need.
Grab a grown-up!
Take the lid off your bottle and crush it, then cut off the top third. You can put the lid back on now.
Make a hole on either side near the top of the bottle, by pushing the point of the compass through into some sticky tack. Then make the holes bigger by poking a pencil through. Push a strip of felt into each side, leaving some felt sticking out. The felt will act like roots, pulling water up into the soil.
TOP TIP: You might want to add a couple of extra holes, in case there are any drainage issues!
With the lid pointing downwards, slide your planter into the bottom of the bottle. If the felt doesn't touch the bottom, you'll need to cut the bottom of the bottle down to size.
Put soil in the top part, and half a cup of water in the bottom. Now you can decorate your planter! You can print one of our Blue Peter colour-in templates, or do your own thing!
All you need to do now is carefully place your seeds on the soil and gently shake the planter so they're covered.