A fan is a component of a dehumidifier, you shouldn't need an additional fan. I'm pasting this from the interwebs because I'm too lazy to type it out in my own words:
How do all these parts fit together to pull moisture from the air? It's fairly simple, but very effective:
A fan collects air from the surrounding area and pulls it into the dehumidifier.
As the air passes through, it comes into contact with the dehumidifier's cooled coils. These coils use condensation to pull moisture from the air. The collected moisture remains on the coils and drips into the dehumidifier's reservoir.
The dehumidifier reheats the air and exhausts it back into the room.
You will need to keep the doors and windows closed, though. Otherwise it would be the same as running an air conditioner with open windows and doors - it won't work.
Most dehumidifiers have a readout showing the RH. I would recommend to not rely solely on the one built into the unit but to buy a cheap hygrometer to monitor the humidity as accurately as possible. Something like this:
https://www.hammondhardware.com/p/springfield-digital-humidity-temperature-monitor-071589039354