There is no way of translating words into Navajo instantly online, unlike with many other languages. Navajo has less than half a million speaker worldwide, given that it's a predominantly South American-spoken language. There are also some speakers of the language found in Canada. Translating online is usually easy but due to the relatively small amount of people who speak the language there is no online instant translation service - hence, I cannot provide you with an answer.
You could also try and use human translation services found on websites like www.freetranslation.com. Whilst this website is able to provide you with instant translation services, where you simply type words into one box and it will be translated instantly and provided to you in the next box, the website also provides human translation services. You will pay a small fee for the person that is providing the work, but you will be provided with a translation that is more accurate (which is useful if you are translating more than couple of words) and sometimes you are able to obtain a translation to a language that is not found on the instant service - hence, you may be able to find a human translation service that will translate to Navajo.
- What to do
You could also try and use human translation services found on websites like www.freetranslation.com. Whilst this website is able to provide you with instant translation services, where you simply type words into one box and it will be translated instantly and provided to you in the next box, the website also provides human translation services. You will pay a small fee for the person that is providing the work, but you will be provided with a translation that is more accurate (which is useful if you are translating more than couple of words) and sometimes you are able to obtain a translation to a language that is not found on the instant service - hence, you may be able to find a human translation service that will translate to Navajo.