Also, to install iOS 14 beta 1 you must have a computer with macOS operating system with installed program Xcode 11 beta (7 GB), or macOS 10.15.
Or you can install a special package instead of installing Xcode 11.
Windows users will have to install a virtual machine with macOS, or use the special instructions for installing iOS 14 from a Windows computer.
How to download and install iOS 14 Beta 1
Step 1: First you need to register with the Apple developer program at https://developer.apple.com/programs/. If you are already registered, proceed to the next step.
Step 2: Log in to the site using your Apple ID: https://developer.apple.com/account/.
Step 3: You need to find out the UDID of your device. Connect it to your computer, launch iTunes, and then click on the serial number in the device information to display the UDID. Copy the number.
Step 4: In the Account section, select Certificates, Identifiers & Profiles.
In the left pane, click Devices. On the right, click “+”, and then insert the UDID of your device.
Step 5: When the UDID is added, go to developer.apple.com/download/.
Select your device from the menu to download the iOS 14 beta 1 file.
Step 6: Extract the .ipsip file from the .zip archive for installation.
Step 7: Make sure you have the latest version of iTunes. After that, run the program, while connecting the device to the computer.
Step 8: On a Mac, hold down the Alt key, on a Windows PC, use the Shift key and click Restore iPhone. Select the iOS 14 beta 1 file you downloaded earlier.
Step 9: Now wait while iTunes installs iOS 14 beta on your iPhone, iPad, or iPod touch. It will take some time. After installation, your device will reboot.
Alternative method (IPSW links)
You can download it for your device from the link below. In this case, the installation process will be the same, starting from step 7, you just need to select the downloaded update file.
Make sure that you download the file specifically for your device model, because otherwise you will not be able to install the update.