how to install xcom files ?

[elcrabo7]

i'm actualy trying to install xcom files but i don't know why it don't work ....
actualy i have the lastest version of open xcom extended and xcom files
i have installed xcom files in the mods's folder but it doesn't appear in the possible mode playable (on the other hand it appear in the regular open xcom it appear but don't work.then I see a message telling me to look if I have the latest version that i have)
What did I do wrong?

[Solarius Scorch]

You're probably trying to run it as a mod, while it is recognized by the engine as a separate X-Com game, like TFTD. So, use the menu dropdown instead.