A Calathea plant is that likes to be moist. You want to water your plant often enough that the soil remains moist.
If it isn’t getting enough water the plant will tell you with drooping leaves or crispy tips.
This doesn’t mean overwatering though. Even though you don’t want to wait until the soil becomes bone dry until you water it, you also don’t want it to be sopping wet all the time. The soil needs to dry out a bit between waterings or the plant can become overwatered.
You can get a good feel for this by feeling the top few inches of soil with your fingers, when you feel it drying out give it a drink. And when you do water your Calathea make sure you do so thoroughly.
If you don’t trust your fingers to measure the moisture correctly then why not consider buying a moisture stick to detect the levels in the soil. This can be a big help for beginners who aren’t sure what moist actually means. We recommened Sustee!
Another way to prevent your soil from becoming too wet when watering try mixing in perlite with your potting soil.