Since I don’t know the specs, I can’t be more specific. But assuming it has at least a USB port (hopefully USB 2.0), and relatively modern OS (XP or better), you can buy and install a USB wireless adapter.
I specifically selected a mini just to show how unobtrusive these can be if chosen wisely. OTOH, it might not have quite the range of others. Something like the Alfa series would be the other extreme, long range and in your face.
If it’s so old it only has an ethernet port (no USB), search for a wireless ethernet bridge (aka, client bridge, gaming adapter, ethernet converter). Such a device can turn ANY wired device into a wireless one. The only downside is that it’s bit awkward to manage for a laptop (some ppl mind, other don’t). But without USB, that’s the only option left.