SRV or service record is specifying service at specific Port in domain name system. Protocol like SIP require this to be setup.
If you are planning to use office 365 then SRV will have to be setup at your DNS provider.
Format of SRV record is
_service._proto.name. TTL priority weight port target.
All these values will be provided by service provider who is requesting SRV and you just need to punch them in DNS manager.
Please follow these steps to setup SRV record using cPanel
1) Login to cPanel and Visit Advanced DNS Zone Manager in Domains section.
If its not available then you will have to request your hosting company to enable it.
2) Select SRV Record from Drop Down Box.
3) Now in Name field you need to club service + protocol + your domain name as _service._protocol.domain
For example is service is _sip and protocol is _tls with your domain as domain.com then Name record will be
_sip._tls.domain.com
cPanel will automatically fill your domain if you just enter service and protocol as _sip._tls
Rest of the fields are self explanatory and enter TTL, Priority, Weight, Port, Target as provided by service provider.