You can find information regarding first startup in our wiki:https://wiki.mikrotik.com/wiki/Manual:F ... me_startup
Knowing the model you have would help a lot. But basically, if re-seller has not changed the default-settings:
1) ether1 works as a WAN connection that you use towards your ISP, it has DHCP-Client built in and will PAT all traffic towards it from your LAN/WLAN interfaces
2) The default DHCP service running on your LAN/WLAN subnet is 192.168.88.0/24 where 192.168.88.1 is the gateway
3) Use your browser to connect to your device, just input 192.168.88.1 in the web url bar: as described in https://wiki.mikrotik.com/wiki/Manual:I ... figuration
*Other ways of connecting to the device are possible, like WinBox, Serial, Telnet, SSH etc.
I'd suggest for you to read some topics that you are interested in from our wiki: https://wiki.mikrotik.com/wiki/Manual:TOC