You need to know the technology of your provider. RouterOS offers you
# L2TP client
/interface l2tp-client add name="my-provider" connect-to="ip" user="myusername" password="mypassword"
# Open VPN client
/interface ovpn-client add... #same options
# SSTP client
/interface sstp-client add... #same options
# PPTO client
/interface pptp-client add... #same options
This pseudocode is for the terminal. In the WebFig interface they are under Interfaces -> Add new drop down
They all are based on PPP, and share the /ppp profile if they gave you any special ppp options, etc.
They also have additional parameters, depending on thecnology: certificates, ipsec stuff...
You can also manufacture yourself some other vpn alternatives, using things like ipsec, ipip tunnels, eoip, ... but the most commons are the ones above.