How to change ttl on my router?

So i got a gl-MT300N-V2 and i’m wondering how to change the ttl on it.

i did some googling and found this line on this forum
iptables -t mangle -I POSTROUTING 1 -j TTL --ttl-set 65

but i can’t figure out how to enter it anywhere

Try to add to the end of /etc/rc.local.

Yeah but how do I get to that file to edit it?

Try SSH to the router - GL.iNet Docs

Alright not home right now but I’ll try later thanks

If the router disconnects and then connects to other WAN or WWAN, ttl change for devices after the reconnect will be flushed with the new firewall restart? I believe his line is put in /etc/firewall.user maybe you meant this one for rc.local
echo 65 > /proc/sys/net/ipv4/ip_default_ttl