Try to use the following code within a Script Editor / Content Editor:


     <script>
    function openDialog(pageUrl) { 
    var options = {
        url: pageUrl,
        title: 'Title of the Dialog',
        allowMaximize: false,
        showClose: true,
        width: 500,
        height: 500
    };
    SP.SOD.execute('sp.ui.dialog.js', 'SP.UI.ModalDialog.showModalDialog', options);       
    }
      
    </script> 
    <a href="#" onclick="openDialog('http://SharePointSite/Lists/WebEvents/NewForm.aspx');">New Form</a>

Note : 

- To show `Maximize button` set `allowMaximize: true`,


OutPut:

[![enter image description here][1]][1]

Check also the detail steps that matched with your situation at [Open a link via Modal Dialog in SharePoint][2]


  [1]: https://i.sstatic.net/YqflE.gif
  [2]: https://blog.devoworx.net/2016/08/13/open-link-via-modal-dialog-sharepoint/