1) you can launch an instance using a preconfigured AMI
2) you can install it manually on your server from the scratch.
3) You can use cloudformation default template to launch an instance with wordpress
In this tutorial am going to explain, how to install WordPress on amazon Ubuntu instance from scratch.
1. Launch an Ubuntu Instance: Follow this tutorial How To launch an Ubuntu Instance on Amzon EC2
2.Connect the instance using putty : Follow this tutorial to do that How To connect Amzon EC2 ubuntu Instance Using Putty
3.Update the Server: Once you connect the connect to the server using putty ,you have to update the server.
sudo apt-get update
You can set up the lamp server using a single command or you can install all the packages seperately. To install lamp server , execute the following command.
sudo apt-get install lamp-server^
The above command will install Php ,Mysql, and Apache. You have to install phpmyadmin separately. For that i have given the code at step 7. If you are going to install LAMP server using the above command, then skip steps 4, 5 and 6.
sudo apt-get install mysql-server mysql-client libmysqlclient15-dev
sudo apt-get install apache2 apache2-doc apache2-mpm-prefork apache2-utils libexpat1 ssl-cert
sudo apt-get install libapache2-mod-php5 php5 php5-common php5-curl php5-dev php5-gd php5-idn php-pear php5-imagick php5-mcrypt php5-mysql php5-ps php5-pspell php5-recode php5-xsl
sudo apt-get install phpmyadmin
sudo wget http://wordpress.org/latest.tar.gz
sudo tar -zxvf latest.tar.gz
16. Click “run and install”
17. Login to WordPress using the username and password that you have created during installation process.
Thats it !! your WordPress installation is done. Now you can manage your WordPress site using its dashboard.