how can i set environment variable in droplet? (not using app platform)

I’m now trying to deploy my app using droplet. Is that okay to put all of environment variables(i.e. dbpassword) in .env file because i’m the only one who can access to my server with ssh and passphrase?

Or is there any other methods that I need to do for security issues? Anyone can see my environment variables in my website if I just put environment variables in .env file?

I saw an option in “Launch Your App” about environment variables to secure. So I’m wondering whether i should do something to keep my sensitive enviroment variables in droplet.