Creating pointers to keys on SmartCard

Creating pointers to keys on SmartCard

I am new to OpenPGP and SmartCards but I cannot find how to do a fairly straight-forward task.

I am trying to sign a file with a private key stored on a YubiKey device.

Here is my session:

$ gpg --card-status
Reader ...........: Yubico Yubikey 4 OTP U2F CCID 00 00
Application ID ...: D2760001240102010006096334120000
Version ..........: 2.1
Manufacturer .....: Yubico
Serial number ....: 09633412
Name of cardholder: [not set]
Language prefs ...: [not set]
Sex ..............: unspecified
URL of public key : [not set]
Login data .......: [not set]
Signature PIN ....: not forced
Key attributes ...: rsa2048 rsa2048 rsa2048
Max. PIN lengths .: 127 127 127
PIN retry counter : 3 0 3
Signature counter : 3
Signature key ....: B692 4360 F06A AB92 1B9A  3E6D 3850 24E1 EE26 F6D9
  created ....: 2019-05-14 14:44:27
Encryption key....: [none]
Authentication key: B692 4360 F06A AB92 1B9A  3E6D 3850 24E1 EE26 F6D9
  created ....: 2019-05-14 14:44:27
General key info..: [none]
$
$ gpg -K
$
$ gpg --list-keys
$
$ gpg --with-subkey-fingerprint -K
$
$ gpg --refresh-keys
$ gpg --list-keys
$

I looked at some posts like this one: Create backup Yubikey with identical PGP keys but I am still not sure what I am doing wrong.

All I need to is somehow use the signature key to sign a file via

gpg --sign -u <key-id> somefile.txt

I need to somehow create a pointer in my local keyring to the Signature key and figure out its id.

I am using gpg (GnuPG) 2.2.12 and libgcrypt 1.8.4

Any suggestions?