RustDesk is an open-source remote desktop software built in Rust. To connect to RustDesk by IP address, you will need to:

1. Open the RustDesk client on the device you want to control.
2. Click on the Menu button (three dots) in the top right corner.
3. Select Settings.
4. In the Settings window, scroll down to the Advanced section.
5. Under Direct IP connections, enable the Enable direct IP connections option.
6. Enter the IP address of the device you want to control in the Host IP address field.
7. Click on the Save button.

Once you have saved the settings, you can connect to the device by IP address by entering the IP address in the Address field in the RustDesk client.

Note: The direct IP connection option is disabled by default for security reasons. You should only enable this option if you trust the device you are connecting to.

Here are the steps in more detail:

1. On the device you want to control, open the RustDesk client.
2. Click on the Menu button (three dots) in the top right corner.
3. Select Settings.
4. In the Settings window, scroll down to the Advanced section.
5. Under Direct IP connections, enable the Enable direct IP connections option.
6. Enter the IP address of the device you want to control in the Host IP address field.
7. Click on the Save button.

Now, on the device you want to connect from, open the RustDesk client and enter the IP address of the device you want to control in the Address field. Click on the Connect button to connect to the device.

Note: The direct IP connection option is disabled by default for security reasons. You should only enable this option if you trust the device you are connecting to.