By LAN, do you mean a personal network you set up, or is this a corporate LAN? If it is a corporate LAN, you'll need to follow whatever procedure(s) may be in place to add a new device to the network. In some places, it's a matter of making sure the wall jack is wired to a switch port, then using a cable from that jack to the LAN; little more than for a home network. In other places, there's the matter of security software being installed and verified, possible static IP address assignment, entry of your machine's MAC address into an ACL list, creation of a machine account in Active Directory, and/or other considerations.
If it is a personal LAN, for example using a router, typically all you need to do is connect a RJ45 Ethernet cable from the laptop to a port on the router. By default, the router will be a DHCP host and will assign an IP address to your laptop. It really should be that simple. If there are resources on that network (e.g. shares or printers on other PCs) that you want to add, you may need to join an existing Homegroup (or older style Workgroup). If a network printer is attached, you may need to make sure it isn't asleep (e.g. power cycle it) so your laptop can find it the first time.