Every reloadable card is different but most of them uses the same methods to load cash onto the card. Below are a couple of common methods to add money to your card.
Reload Pack - A reload pack is a paper card that you buy from the store. Examples of reload packs are MoneyPak & REloadit. Visit the MoneyPak website and check if your prepaid card is supported. PayPal Digitize Cash is a little different because you have to generate a barcode from PayPal and provide the cashier with the code.
Reload at Register - For the vast majority of prepaid cards you are able to add money to the card by simply going to the cashier at selected retail stores (Walgreens, CVS, Rite Aid, 7-Eleven etc view full list) and request to add money to your card. This method comes with a fee that varies between different prepaid cards but is usually around $4-5. Green Dot, the leader in the prepaid card coined this service "Reload @ Register".
Direct Deposit - If you are paid regularly through some sort of program or a job this is the best option. Most prepaid cards are packaged with a direct deposit form, that the cardholder fills out and provide to their program or job.
Card to Card Transfer - If you already have another active prepaid card that have money available in the balance, you can link that card to another prepaid card. This is done by logging into the prepaid account that you wish to transfer money to. There should be an option somewhere in the dashboard that says "link card", "link bank" "transfer money", "move money" or something similar. Jot down the information from the card that has money into the required fields (account number, routing number and bank & cardholder name is the information usually required)