On this page you can see all the PCs on the LAN segment. Each PC is qualified to be either "dynamic" (PC which obtained a lease from this router) or "static" (PC which has a manually configured IP address).
You can add "static" IP address (belonging to the network segment of the router LAN IP address). Any existing static entry falling within DHCP server range can be deleted and the IP address would be made available for future allocation.
Once an IP address is allocated it shows up in the list of LAN clients as "dynamic" entry. Any dynamic entry can be converted into static by using "reserve" checkbox.
Note: dynamic clients show up in the list only when DHCP server is running.