This assumes you have generated an OAuth Bearer Token using the ServiceNow REST API.

Here is an example of how to GEt a change ticket using curl, replacing abc123 with your Bearer token.

curl \
--request GET \
--header "Authorization: Bearer abc123" \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--url "https://acme.service-now.com/api/sn_chg_rest/change?number=CHG00123456"

Or using the short description of the change.

curl \
--request GET \
--header "Authorization: Bearer abc123" \
--header "Accept: application/json" \
--header "Content-Type: application/json" \
--url "https://acme.service-now.com/api/sn_chg_rest/change?short_description=my%20short%20description"