You might as well take them from there if you want limpets, but most of the time people pick them up through the "Advanced Maintenance -> Restock" menu, where you can buy as many as you want for 101 credits each at almost any station. They'll move between ships like other cargo if you have enough cargo space in the new ship.
To deploy them:
- buy a Collector Limpet Controller
- assign it to a fire group and fire button
- target nothing (deselect your current target), fire the controller, open your cargo hatch, and watch the limpet pick stuff up for you. Larger controllers can have more limpets out at once, but for materials collection, generally one limpet is fast enough, and two is definitely as many as you need.
The reason you target nothing is that if you fire a Collector with something targeted, the limpet will specifically go for that object only, pick it up, return it, then self-destruct. Great if there was literally only one thing you wanted, but generally it just means you get through a lot more limpets than otherwise