It's very easy, you'll install KeepassXC on both pcs, and as you can read here from their docs, the first time you'll create a brand new database (usually a .kdbx file). You can create as many as you want actually, and you can move or copy those files around, so experiment without worries. Any compatible keepass software will be able to open these databases (as long as you have the secrets needed for each one like its key or its master password..).

KeepassXC also remembers the last file locations, so the next times you open the program it should look for the db in your pen drive and immediately ask for the master password. The KeepassXC in your different pcs are indipendent, but you can edit a common file, just like we would with a word document for example.