Send value to show Function from Form Laravel

I have a Form in Blade and I need search a user based on his username. I want to use the show() function in controller. my form Looks like this

{!! Form::open(array('route' => 'userlookup.search', 'id' => 'userSearch', 'class' => 'needs-validation')) !!}

                    <div class="input-group mb-3">
                        <div class="input-group-prepend">
                            {!! Form::select('searchBy', array('UIN' => 'UIN', 'pNumber' => 'Permit Number', 'tNumber' => 'Transaction Number'), 'UIN', ['class' => 'form-control']); !!}
                            {!! Form::text('searchInput', '', array('class' => 'form-control', 'id' => 'searchInput')) !!}
                        </div>                            
                    </div>

                    <div class="input-group">
                        
                    </div>

                

and I want to send the value from the input field to show function to search the user and redirect to view. I have looked at couple of answers but each one gives me answer using which does not work here.

Thank You.

via Chebli Mohamed