I took a look at your CRM_NewLead(2) screen and found that you put the LeadSource_RecordID field on the screen and just renamed the Caption to Lead Source Name (see below). So the Lead Source Name field doesn't actually exist in your Customer table. You'll first need to create the text field in your Customer table in order for you to be able to type data into that field and save it for each customer/lead record. To add a new field to a table go to Customize > Tables/Fields > click on the name of the table, i.e. Customer > add your new field.
Additionally, all RecordID fields are used specifically for identifying and associating specific records to one another. In order to prevent records being messed around with, we do not allow these fields to be modified then saved. RecordID's are stored as numbers which explains why you can only type numbers into the field, however, Method won't save the changes you make to that field.
I would strongly recommend you watch our Webinars, in particular, the Customization webinars (near the bottom of the page) so you get a better understanding of how to customize tables/screens in Method. Another great resource available is the Customization section of our Help Center Knowledge Base.
- Ashur