You can do this in many ways, one is using semantic ui. Add this script file
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.1.8/semantic.min.css" >
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.0.0-beta1/jquery.min.js"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/semantic-ui/2.1.8/semantic.min.js"></script>
<script>
$('.ui.fluid.dropdown')
.dropdown({
maxSelections: 5
})
</script>
<select class="ui fluid dropdown">
<option value="">Skills</option>
</select>
For better understanding please go through this example Bootstrap multiselect is not working when i bind the data from response in Angularjs
If you want in Bootstrap4 please have a look at this Bootstrap 4 multiselect dropdown