Hello guys,
Im in istanbul community, so i wanted to use or connect to gateways that i see. We have 4 gateways as a community but can i use them without doing anything?
Firstly, to clarify - you dont join a gateway with LoRaWAN you join a network, unlike WI-Fi where you associate with/join an access point. LoRaWAN is a broadcast technology where all gatewas in range receive your nodes messages.
This then gives you a clue on how to proceed…
Simply set up your node and start to work with TTN/LoRaWAN…if your nodes fail to join the network and or fails to get data through to your application/device page then possibly you are not in range of any of the GW’s - dont forget to allow for ground topology, building clutter or obstructions when ‘guessing’ if you should have coverage. How far away are the GW’s? Do you have map/overview to assist in making the judgement? If no success then next step would be to move closer to one of the GW’s to test your node - say 100-500m away…if you still have no success then it may be you start to suspect your set-up - check configuration, device keys, console registration details, LoRaWAN Phy settings, frequency plan & channel settings, etc. Note: all this gets A LOT easier if you get your own cheap GW where you can see GW logs to check GW is picking up your messages correctly, alongside any of your node logs, and passing back any network messages (join accepts etc. in the case of OTAA)…and you are also helping expand the networks coverage at same time! 
Try this and come back with results and problems seen - note details are important (hardware/firmware/physical so is reading the docmentation and using forum search to self help as many issues have been addressed many times before and volunteers tend to be more forthcoming with users who have demonstrated willingness to help themselves first before repeating previously covered issues… 
Thank you so much, I am gonna try it today.