It's an actual Lighting Node has all all the important properties thereof -- it's not a "shared wallet" or "wallet service"..... By "top it up" you might mean "deposit BTC so you can spend it as Lightning". The most low-level way to do that would be to deposit BTC onchain to the Lightning Node, and then open your own channel. But to do this with under, like 150,000 sats is not really a great idea. So another thing you can do is get an *inbound* channel, and then follow either of these "get outbound capacity" strategies here: https://rizful.com/docs/balances-and-capacities#outbound-capacity

You could also "swap in" with Boltz, but that isn't my usual strategy...