If you don't have enough inbound capacity, you must either rebalance a channel by sending out sats to another node (another wallet), possibly swapping to on-chain or you must ask another node to open a new channel to your node with enough inbound capacity. Zeus, Phoenix, Breez and Blixt use various technics and services to automarically open this new channel but you habe to pay for the on-chain transaction + some fees (usually). Depending how the mempool is busy, these on-chain transactions can cost 2000-3000 sats or 30'000-50'000 sats.