wired LAN to Wireless

Please excuse this naive question – but I have access to a wired ethernet LAN in an appartment block and want to find out if it is possible to make use of this by adding a “box” of some form that would give me a wireless network in my appartment? If so what sort of box do I need?

Also I live in an isolated house when home with no neighbours nearby– the strength of the BT suppplied wireless router is too weak to reach all the rooms I need to use the wireless network– what sort of booster can I buy? There is no problem with interference with other networks as there can be none for several miles and clearly hotels and other institutions have stronger wireless networks.

Many thanks
Mark