Importing Opportunities with Dataloader from MuleSoft, also known as Dataloader.io

To import Opportunities using Dataloader from MuleSoft, begin by going to https://dataloader.io/ and click the Login with Salesforce button in the upper right. 

The following example can be used for a test import while going through the following steps. If you do not have an Account or Contact with the values in the example, simply change the values to the names of an Account and Contact that are in your org. To use this example for a test import, copy and paste the values below into an Excel or Numbers worksheet then save it as a .csv file.
 

Now that we have a test .csv file, in Dataloader from MuleSoft (Dataloader.io):

1. Click New Task at the top-left corner of the screen then select Import
2. Ensure Insert is selected in the Operation section
3. Search and then select Opportunity in the Object section
4. Click Next
5. Upload your .csv file
6. Map your Opportunity Name .csv column to the Name field
7. Map your Account name .csv column to the Account ID field
8. Select the Lookup Via checkbox under Account ID then select Account Name in the dropdown field
9. Leave your Contact .csv column unmapped
10. Map your Stage .csv column to the Stage field
11. Map your Close Date .csv column to the Close Date field
12. Click Next
13. If the edition of Salesforce that you are using is the Essentials edition, ensure that the option for API Mode has 'Use Batch API with 200 records per request' selected before clicking Save & Run
14. Click Run in the pop-up window

After the import is completed, the next step is to perform an import that relates the Opportunity to its associated Contact in Dataloader from MuleSoft (Dataloader.io):

1. Click New Task on the top-left corner of the screen then select Import
2. Ensure Insert is selected in the Operation section
3. Search for then select Opportunity Contact Role in the Object section
4. Click Next
5. Upload your .csv file
6. Map your Opportunity Name .csv column to the Opportunity ID field
7. Select the Lookup Via checkbox under Opportunity ID then select Name in the dropdown field
8. Map your Contact name .csv column to the Contact ID field
9. Click the Lookup Via checkbox under Contact ID then select Full Name in the dropdown field
10. Click Next
11. If the edition of Salesforce that you are using is the Essentials edition, ensure that the option for API Mode has 'Use Batch API with 200 records per request' selected before clicking Save & Run
12. Click Run in the pop-up window

After your import is completed, you can log in to your Salesforce org to confirm:

1. Your Opportunity was successfully imported
2. Your Opportunity is related to the correct Account
3. Your Opportunity is related to the correct Contact After confirming that the import worked as expected, proceed with uploading any further data using the same steps.

For more information on importing using Dataloader from Mulesoft (Dataloader.io), please review the following resources:

1. Importing into Salesforce 
2. Using Import Lookups  
3. Dataloader.io Free 
4. Mulesoft and Support for Dataloader.io