How to add css/width in sidecar column?

Hello everyone,

I have custom code to create side car. I want to apply css(width) for table th column tp make wider? But unable to add it. Please help if hava any solution.

My Code in side car:

ii_wpLayout = this.layout.layout.getComponent("dashboard-pane").getComponent("ii-wp-selection");
ii_wpView = ii_wpLayout.getComponent("main-pane").getComponent("filterpanel").getComponent("ii-wp-selection");
 $('.table thead th span').css('width', '170px !important');
Another File where am applying:
custom_directory\modules\myModule\clients\base\views\ii-wp-selection\ii-wp-selection.js
({
    extendsFrom: "MultiSelectionListView",
    allowedFields: ["name", "internal_barcode","storage_condition","allowed_storage_conditions","allowed_storage_medium","location_building","location_room","location_equipment","location_shelf","location_cabinet"],
    initialize: function () {
        this._super("initialize", arguments);
        this.collection.reset();
    },
    render: function () {
        this._super("render", arguments);
        this.layout.$el.parent().addClass("span12 ii_wp_selection");
         $('.table thead th span').css('width', '170px !important');
    },
    addActions: function () {
        this._super("addActions");
        this.rightColumns = [];
        this.meta.panels[0].fields = _.filter(this.meta.panels[0].fields, function filterFields(field) {
            return this.allowedFields.indexOf(field.name) !== -1;
        }.bind(this));
    }
});
Thanks,
Laxmichand saini