How do I manually add an ERC20?

I'm new to the world of cryptocurrencies and I'm having some trouble understanding how to manually add an ERC20 token to my wallet. I've heard that this process can be quite technical and requires some specific steps to follow. Could you please explain to me in detail how I can do this? I'd appreciate it if you could break down the process step by step, including any necessary prerequisites or things I should be aware of before attempting this. Also, is there any specific wallet that you would recommend for this purpose? I'm looking for a secure and user-friendly option. Thank you in advance for your help!