To secure your online accounts from being accessed through public Wi-Fi networks:

1. Set a strong password that can’t be easily guessed and make sure that they are unique from each other.
2. Change your passwords periodically.
3. Avoid accessing any sensitive personal information or accounts while connected to a public Wi-Fi network.
4. Enable two-factor authentication (also known as two-step verification). This requires an additional code as authentication when signing in to an online account.
5. Use a reliable virtual private network (VPN). This encrypts the data going between the device and the network, protecting it from malicious or unauthorised access.