Not sure how to configure signature element

[LeonAdato]

Background/Context:
I'm creating a simple php script that uses curl to retrieve info from a remote WooCommerce site via the API as a proof of concept.

Issue:
I'm not seeing how to generate discrete oauth elements like signature

Specifics:
using Postman, the curl command includes these parameters:
CURLOPT_URL => 'http://MYWEBSITE/wp-json/wc/v3/
?oauth_consumer_key=<THE KEY>
&oauth_signature_method=HMAC-SHA1
&oauth_timestamp=<TIMESTAMP>
&oauth_nonce=<NONCE>
&oauth_version=1.0
&oauth_signature=<SIGNATURE>',

I can handle everything except the signature. Using the php oauth library, I would do this:
$oauth = new OAuth($this->consumerKey,$this->consumerSecret);
$oauth->setToken($this->token,$this->tokenSecret);
$url = $this->'<THE WEBSITE>';
$nonce = mt_rand();
$timestamp = time();
$oauth->setTimestamp($timestamp);
$oauth->setNonce($nonce);
$sig = $oauth->generateSignature('GET',$url);

I'm trying to model the same behavior with this library, but I can't see an example that grabs a signature. I'm probably just overlooking it.

THank you in advance!