TLS Auth file, which extension?

[arbrkic]

I am trying to connect android phone via OPENVPN for android to our company's VPN Server.
We are using TLS Auth, and I copied the key and saved it into file key.crt .

Hovewer, when I try to open this key in OPENVPN client it does not allow me, it is grey, like extension is not good.
Any idea how can I import TLS key to OPENVPN client? Which extension should I use? Is there any way to enter it manually ?

Thank You

[Traffic]

We are using TLS Auth, and I copied the key and saved it into file key.crt

That is not the way to do it ..

You need to make an inline config file which contains all of your certificates and keys like so:
https://community.openvpn.net/openvpn/wiki/IOSinline