How do i put textbox with a text exactly below the next one? css&html

I'm trying to put the text box with the text before and it doesn't work. I tried with float and its works but stick the text together... please help (:

 <div class="optionContainer">
        
        <div class="firstName">
            <label for="fname">First Name*</label>
            <input type="text" id="fname" name="fname">
    </div>
        
        <div class="LastName">
            <label for="lname">Last Name*</label>
            <input type="text" id="lname" name="lname">
    </div>
    
    </div>