How do I add a custom field in Vtiger CRM?

You can add custom fields to a module by creating custom fields and blocks.

Follow these steps to access module management settings:
Step 1: Accessing the Module Management SettingsTo build a module, you must specify its basic details. 

6. Enter or select the following information to add information for the new module:
   1. Module Label - Specify the module name. For example, Workforce
   2. Singular Module Label - Specify the module name in the singular form. For example, if the module name is Contacts, then Contact is its singular form. The singular form of Workforce is Workforce.
   3. Select App Category - Select the app under which you want to create the module. For instance, you can create Workforce under Projects.
   4. Record Identifier - Specify the label by which you want to identify the module’s records. For example, Workforce Records are identified by Workforce Name.
7. Click the Create button.

Once a module is created, you will be moved to the next section, Blocks, and Fields.

Step 3: Creating Blocks and Fields
Note: Some fields are provided by default in the Basic Information block. You can also create custom fields and blocks if needed. For example, you can add under Basic Information, Address Details under Basic Information, etc. 

8. Click the +Add Block button to create a new block. An Add Block window opens.
   1. Enter the Block Name.
   2. Select Add After from the drop-down. Choose the existing block, after which you want to add the new block. 
   3. Click Save.
9. Click the +Add Custom Field button in the newly created block.
   1. Select the Field type. For example, Phone for a phone number, Text for a name, etc.
   2. Enter the Label name. 
   3. Enter Min characters allowed.
   4. Enter Max characters allowed.
   5. Enter a default value for the field.
   6. Set the field properties:
      1. Mandatory Field - If enabled, entering a value for the field becomes mandatory.
      2. +Quick Create - The field becomes available under Quick Create if enabled. 
      3. Key Field View - If enabled, the field appears in the Key Fields section of a contact’s Summary View.
      4. Header View -If enabled, the field appears in the Header section of a contact’s Summary View.
      5. Mass Edit - If enabled, you can perform a mass edit action on the field.