You can install the touch driver for 3.5″touch screen on an existing system, but it just supports raspbian and ubuntu system.
Raspberry Pi must be connected to the Internet,and you can control it through ssh,vnc, Remote desktop or the other big HDMI display.
First, change the password of the root account and enable the root account:：
sudo passwd root
sudo passwd –unlock root
Step 1:Open the command terminal,Enter the following commands to download the 3.5″touch screen driver;
sudo git clone https://github.com/kedei/LCD_driver
Step 2:Change file permissions;
sudo chmod -R 777 LCD_driver
Step 3:Enter the folder;
Step 4:Install the driver, RaspberryPi will auto reboot ;
You can use the following command to rotate the screen
DownLoad Url osoyoo.com