where is the "navigate" menu

Go to your list of activities. Hit Add. Scroll down until you see navigate. Add it to your quick list of activities. Go back and navigate. You can also add activities through your phones garmin connect app if you have it installed and synched with your watch.

"go to your list of activities"

do you mean "press the gps button"?

if yes, i have only a list of activities but not any "add" choice.

or do you mean something else? how to go to my list of activities?

Yes press the gps button to see your list of activities. Usually the last item is "add" if you don't see this I'm guessing you have never added any activities. Add one at random. Maybe a run or walk. Then go back to the main watch face and go to your list of activities again (press gps button). You should now only see "run" and "add". Add the activity you want. The first time adding activities I believe gives you a reduced list of common activities to try out. If you still don't see it have you connected you watch to garmin connect? You can also add and delete activities through connect you may find this easier. If you still cant figure it out I'm at a loss.

i have found in another forum someone that said that we have to choose the "tactical" activity 1st to see the navigate choice and the others

i have done it and indeed it displayed the navigate option

but when i came back to the activities list, they were all lost, only the tactical was available.

but its ok. now i can even see the add button and add the activities lost lol^^

thank you for your help

Alternatively, you can navigate to a saved location by using any of the GPS enabled activities (e.g. run, walk, hike, bike, etc.).  

1. From the watch face, press GPS button
2. Select an outdoor/GPS enabled activity
3. Press up button (left-middle) to enter options menu
4. Scroll (using up or down button) to Navigation
5. Press GPS button
6. Scroll to Saved Locations
7. Select desired Saved Location (GPS button)
8. Select Go To