sfdx force:source:push command can be used to push source to Salesforce Scratch Org.

1. Create a Scratch Org. If you are newbie, please check the following link to create a Salesforce Scratch Org.

How to create Salesforce scratch org using VS Code?

2. Use the following command to push the Metadata to the Scratch Org.

sfdx force:source:push --targetusername test-vhyibssa6me3@example.com

Here, test-vhyibssa6me3@example.com is the username of newly created scratch org.