Well, you probably don't need to access your router's settings for this. You can simply go to the Network and Sharing Center (right-click on your network icon in the bottom right-hand corner or access it through the Control Panel) and then click on "Change Adapter Settings". You would then right-click on your network adapter and click on "Properties", click on "Internet Protocol Version 4" and then click on "Properties" and set both the address and DNS to automatic and hit "OK" to ensure it commits the settings, it may take a few seconds.
You would set static when your router doesn't support DHCP (Dynamic Host Configuration Protocol) meaning it doesn't know how to automatically assign IP addresses, which these days in routers would be a rarity unless it's manually disabled. The advantage to static IP is that the device set with one will be reachable at that same address always meaning other devices don't need to attempt to define where this device is as it will always be at one address. This is particularly useful for network printers and servers, which are accessed by multiple users and must be pointed at by more than one device.; you can keep a consistent list of said devices and what their addresses are and always know that they are accessible at said assigned address. In terms of servers, think of web servers; they should definitely have static IPs as when you type in a website (e.g.: bing.com), DNS has to take that address and translate it to an IP address to get you your page. That IP address corresponds to a server(s) where this website is hosted. If static, then it will always be in one place, easily reachable and available. I like to equate it to a street address, as you keep it the same when you don't move, then your location is easy to find as the address is not changing. The downside to static addresses is that you have to configure them manually and know all your network settings and ensure that no addresses conflict as you cannot have the same address on two PCs in the same network.
Dynamic addresses have the advantage of not really requiring any configuration and are generally picked up from a router. Additionally, they can change and accomodate new devices coming into the network, not requiring you to maintain a list of the current IPs assigned letting the router do the work for you. The downside is they can change and are not always consistent. Although a PC (Windows PC anyway) will try to pull its last used IP address if connecting to the same network, if it's not available, it will simply attempt to pick another IP address that is available.
For the average home network with a wireless router, you can use dynamic addresses. Unless you're experimenting or have some specific reason you'd like to use static addresses, there is no reason to do so. Dynamic addresses will be fine and far less work than configuring each device with a specified IP address. Between ensuring conflicts like this don't occur and also keeping track of who has what IP, dynamic takes the leg work out and lets the router do the work.
