sorry guys but i'm not very good at this so i need help
i have a wifi modem with 4 lan ports in the dining room which is in 1 corner of the 1st floor n my room is in the other corner of the ground floor(diagonaly) i also have a family desktop in the dining room n i'm about to get a pc in my room so how do i get a LAN connection till there?
Just run a cable from an LAN port on the modem/router down to the lower floor and either cable to the machines or attach that cable to a new router configured as an access point (just turn off its DHCP, use the same wireless security type and password, same SSID, and a different radio channel). Something inexpensive like an N TP-Link router will work fine.
If you cannot get a cable down there and your wireless doesn't cover it, you can also use MOCA or powerline in place of the Ethernet cable, although it won't be as fast a connection depending on conditions.
If wireless reaches with a strong signal but you want to use wired, you can place a wireless bridge downstairs and attach Ethernet cables to it.
Just depends on what you have and really want to do.