Any cost any good tutorials?
I don't think that's up to you to determine, and i don't think that it is possible to do yourself, you will need coinomi to add it for you, unless you ofcourse want to hardcode your altcoin into your client-sided coinomi wallet, which seems like a hassle, and will only effect you, not the rest of the userbase of coinomi.
However, you can however manually add certain tokens of the ETH network, READ =
https://coinomi.freshdesk.com/support/solutions/articles/29000009779-how-can-i-add-a-token-that-is-not-in-your-list-of-200-natively-supported-tokens-