Creating a sandbox in Salesforce is not a huge task. You can create a Salesforce sandbox by going through the below listed steps one by one.

1. Go to setup and type sandbox in Quick Find/Search Box.

2. Click on Sandboxes and then click on the new sandbox button to create a new Salesforce sandbox.

3. After clicking the new sandbox button, fill the details for the sandbox like Name and description of your sandbox.

Note- Here we are creating a developer sandbox but you can create a sandbox according to your requirements. Salesforce provides below four types of sandboxes-

• Developer Sandbox- The primary purpose of a Developer sandbox is to provide an environment in which changes under active development can be isolated until those changes are ready to be shared.

• Developer Pro Sandbox- Developer Pro sandbox environments provide the same functionality as Developer sandboxes types do, with increased file and data storage. 

• Partial copy Sandbox- Partial Copy Salesforce sandbox types include all of your organization’s metadata and a sample of your production organization’s data that you define by using a sandbox template. To create a Partial Copy sandbox, you must apply a sandbox template at creation time.

• Full copy Sandbox- Full sandbox environments are a replica of your entire production organization and all its data, including standard and custom object records, documents, attachments, code, settings, and so on.

Note – Make sure that your sandbox name does not contain any space or underscores otherwise you will get the error message as shown in the screenshot below

Note – Please check the Salesforce licenses that are available and needed to create a Salesforce Sandbox before you go ahead to create any sandbox as shown in the below screenshot.

4. Just click on the next button.

Note – The sandbox templates are only available when you are creating a partial sandbox or full copy sandbox so you can give the limit to copy your data from production to sandbox.You can create sandbox templates by following these steps-

1. Click on sandbox templates and then new sandbox template-

2. Enter the name and description of your sandbox template and select the checkbox as you want to copy which data in your sandbox from production.

5. Now if you want to run the apex class after creation of the sandbox you will fill it, otherwise you will leave it blank and click on the create button.

6. Your sandbox is in progress as you can see in the screenshot below the status of the sandbox it is showing Pending.

7. Now your sandbox status is converted from Pending to Activating. You can see this in the screenshot below.

Note – After 15-20 minutes you will receive an email that your sandbox is created and ready to use.

Also for the first time login the user will get the username and password in the mail.

8. Hurrah! Your sandbox is ready to use as you can see the status is completed in the below screenshot.You can login from production after clicking on login as shown below.

Another way to login into sandbox is using test.salesforce.com in URL as shown in below screenshot.

This is how we can create a sandbox in Salesforce and login into it to do the developments and testing before pushing the changes into production org.