In the form editor (/admin/leadforms/{id}) click + Add New Field (or hover a field and use the + before/after buttons). The panel is grouped into Form Questions — Single Line Text, Multiple Line Text, Email, Phone, Date, Time, Number, Single Check box, Multiple Checkboxes, Dropdown List and Radio Select — and General blocks — Text Block, Image and Video. Click a type; its settings panel opens:

• Name (Only shown to admins) — the column header in Results.
• Mandatory toggle (questions only).
• Label (required, with an AI-suggestion button) and label Color.
• Placeholder (Single Line Text, Multiple Line Text, Email only).
• Options — add one option at a time with + for Dropdown List, Multiple Checkboxes and Radio Select; Min/Max Options to choose for Dropdown List and Multiple Checkboxes only.
• Blocks: Title with Show The Title? and Title Color (shared by all block types); Text Block rich-text; Image with Min/Max Height (px/em/rem); Video with Full Size, Video File upload or Video Url, Height and Outer Class.
• Link to A Proposals Field — maps the answer to a proposal field (Proposals module, only on a form that has Link to Proposals turned on).

Click Save. Use the pencil, up/down arrows and trash icons on each field to edit, reorder ("The Field was moved with success") or delete it (deleting also removes that field's answers from stored results).