To install apache :
sudo apt-get install apache2
Once it's installed you have a web server running that can be accessed on your local network.
To check it's running go to your web browser and type 127.0.0.1 and it should come up with a default page.
To access it from other computers on the network we need to find out your local IP address which can be done with:
ifconfig wlan0 | grep "inet addr"
This will give you a output of
inet addr:192.168.0.18 Bcast:192.168.0.255 Mask:255.255.255.0
With your IP being
Now enter this ip on another device on your local network and it should come up with the same default homepage, if you want to set a static IP have a look at this post.