Yes, you can use any icon on Iconfinder as long as you abide by the terms in the license agreement of each icon. The license information will be displayed on the right side on the icon page, as shown below.
Free icons can be used free of charge. They are protected by different license agreements, so you will need to pay attention to that.
Premium icons are paid and are all protected by the Basic License.
If you need more help for licenses, please check our License Overview article.