When you produce a fleet it spawns on your base after you produce it.
There is no such thing as hidden for yourself. You will always see your fleets.
Now for other's players fleets you will have to move 1 of your fleet/ships to that certain's player region to see his fleet and if any others in that region.
It doesnt have to be on the same system. Just region and you will have "scouted" the entire region using the interface map the game offers you. You will see the other players bases.
This is the wrong thread to post such questions.
Post in the Help Center
section of the forum any questions you may have. I see you already made a thread here
and i have answered you there. You can make any other questions there