You can charge your Welcome Suica card (put money on it) in various places, including ticket machines at stations and in convenience stores. Just look for the mark. You can charge your card with cash. You can put up to 20,000 yen on it.

Yes, you can easily "top up" or add money to a Suica card, which is the primary prepaid IC card used for transit and shopping in Japan. If you have a physical plastic card, you can add funds at any "Ticket Vending Machine" or "Fare Adjustment" machine located in virtually every JR East and subway station; these machines typically have an "English" button and only accept cash (Japanese Yen). You cannot use a foreign credit card at these physical machines. However, if you use a Mobile Suica (integrated into Apple Wallet or Google Pay), you can add money directly through your phone using a linked credit or debit card at any time. Additionally, many convenience stores like 7-Eleven, Lawson, and FamilyMart allow you to recharge your card at the counter by asking the clerk for a "charge" and providing cash. Note that the maximum balance a Suica card can hold is 20,000 Yen (approximately $135).