Modal is on the same page. So whatever input field you have inside modal is accessible in your page.

For example you have

<input type=text id=txtName />

You can simply access it using

$(#txtName).val(); 

for Modal code. Here it is done

 <button type=button class=btn btn-info btn-lg data-toggle=modal data-target=#myModal>Open Modal</button>



<!-- Modal -->

  <div id=myModal class=modal fade role=dialog>

    <div class=modal-dialog>



      <!-- Modal content-->

        <div class=modal-content>

          <div class=modal-header>

            <button type=button class=close data-dismiss=modal>&times;</button>

            <h4 class=modal-title>Modal Header</h4>

        </div>

     <div class=modal-body>

       <input type=text id=txtname>

    </div>

  <div class=modal-footer>

    <button type=button class=btn btn-default data-dismiss=modal>Close</button>

  </div>

</div>