How do you add a license to steam with the add license command

you need ASF
https://www.steamgifts.com/discussion/gCxhN/archis-steam-farm-asf-steam-cards-farmer-and-much-more-windowslinuxos-x

The add license command is a command in a program called ASF, which is used to farm cards. Typically you'd only want to use this command if you want to add a license to multiple accounts at the same time (bots) or without physically logging in to your bot.

https://store.steampowered.com/account/registerkey

!addlicense asf 480430 this gives you Hide and Shrike to steam for free

!addlicense command supports 2 different types of numbers, as stated on the wiki: appID and subID.

AppID can be used for free on demand license, and it's typically available for games that are "always" free only.

SubID can be used for temporarily free packages, and this is what you must use if game is normally non-free but temporarily free on the Steam store. In case of always-free games it usually doesn't matter whether you use appID or subID.

Refer to SteamDB for subIDs. Correct !addlicense number for this game is 216184.

If somebody wants a better example to understand what's the difference, then he can check chivalry subs. When the game was offered for free, ASF users could activate subID 164655 in order to get game and card drops (if available) permanently. AppID of 219640 will not work in this case, as game is not free (ASF might reply with OK if you already own it though).

If you're familiar with javascript, there are resources online for how to code in the command yourself. Alternatively, SteamDB has traditionally been the go-to location for premade scripts of that sort (and, if you're just wanting to add a single specific free sub to your account, you can do that with a single button click (in the top right) on its associated SteamDB page). If you're an ASF user, you can instead use it to process the command.

Thanks for all the information .