Where is the data stored for that field? Does it depend on another field in Marketo? If you already know which value to populate, then build a smartlist that shows you the 1800 leads. Select all leads. Under Lead Action, use the "Change Data Value" to populate the field. Other option is to use static list by creating a CSV file of the 1800 leads. Just need 2 columns: email address and your new field. Upload the list.
Thanks so much for the reply Ali!
The data is stored in a CSV file. The file also contains matching information (lead First Name, Last Name, Company and Email Address), which Marketo can use to match the new field data to the appropriate lead.
That's a good idea to create a Smart List. How will Marketo get the information from this CSV file if I create the Smart List and use "Change Data Value" to populate the field? Also, the data I need to populate the leads with is unique for each lead (i.e. I am not populating all 1800 leads with the same data, just unique data from the same field).
You can use a Smart List to segment the your data and then use the "Change Data Value" flow step to update. Depending on the number of unique values you are updating with, this can take a while. But if there are only 4 or 5 different values, then this approach will work.
If you have many values that will be using to update the list with, then the approach would be to import your CSV into the Lead Database. When you do this, all you need is the email address and field you want to update because Marketo only matches/deduplicates on Email Address. Meaning, if you have records who do not have an email address, when you reupload, you will be creating duplicate records.
Thanks Jeff! I tried your second suggestion (because I had many values), and it worked perfectly!
What if the list of leads you are trying to add an extra piece of data to do not have an email address (they were previously uploaded to create PURLs)? I tried using the Marketo Unique Code in place of an email address but it created duplicate records instead of just updating the existing.
I am also trying to append an unique piece of data for each lead (6,000+) so batch updating one at a time with Smart Lists and Change Data Value won't work.