Your current form may include a table where data is input into multiple cells as a group. Tables like this can be translated in FastField by using subforms.
Subforms allow you to capture recurring instances of the same data type. An example of this would be recording an inventory of items with line items. In this scenario, you would create a reusable subform representing a line item input. Let's look at this physical inventory sheet as an example.

Turn a table into a subform
Not all of this table would be included in the subform. Think of the top section as a static section and the item inventory table as a dynamic set of fields.

These top four fields would be translated into numeric, date/time, text, or option list fields and would not be included in the subform but would be included in the main form.
Example:

The part of the table that would be included in the subform would be the Inventory number, item description, purchase price, quantity, and location.

Your subform should look similar to the example below:

Add the subform to your main form
Log in to the Portal using your username and password.
Note
Only the Admin and Builder roles can edit a form.
Open your form, and add the Subform field type.
On the right-side panel, select the subform you have created.
Select Allow Multiple Subform Instances; this will allow you to repeat inputs in the table.
From this point, you can configure the subform field as needed. See Create and use subforms for more details.

In practice, Allow Multiple Subform Instances must be turned on to use the form as an item inventory log effectively. Complete the item inventory subform as many times as needed, then select Submit. Your instances will be queued as shown until you are finished.

Select Submit when you have finished your subform instances.