Go to setting, General tab:
Go to setting, Poller tab:;
After you setting like above, you can create new device to graph in your cacti in device menu. Next you go to devices, and then click add in the right. Lets configuring your devices like here:
Hostname : Your hostname(IP, domain etc)
SNMP Version: Version 1 set the community, version 2 set community like version 1, version 3 set the username and password.
Community: is name, mus be same with the server or devices.
For example: If you use mikrotik device, and your mikrotik set the ip public 202.158.2.xxx. your hostname is 202.158.2.xxx, and you must set the community in the mikrotik(IP >> SNMP >> enable, community : public). In the cacti set the community is public like the mikrotik.
After that, you can create graph from your device with click the Create Graph for this host in the top page. After you click, you will see ethernet or port with vlan in the next page. And then you can choose the port to graph the statistics. If you have choose the port, in the bottom of page you choose in/out bits Total bandwidth. Next and Finnish.
Go to graph trees, you create the trees to input your graph.
Go to devices, select your devices, click graph list. and select your graph and put your graph to your graph trees. That is. It's simple.