This is fast and dirty set of process steps to determine where a stationary reference station antenna (or any GNSS antenna for that matter) is placed. It requires several hours of raw observational data to be collected, and then sending your data set to 3rd parties to determine the position. This will result in a position accurate to within a centimeter or better.
There are many sources that do a better job of explaining this process, how to select a suitable site, and the basics of good surveying practices. You will see a number of very good educational links to such information on the two post-processing sites below, please read them.
Collect the Data
Gather 4+ hours of data from the site.
With SNIP settings, simply log the raw data for the time period desired. Logging on a stream is enabled with a right-click mouse action on that stream. The collected file period defaults to 24 hours but can be set (as well as the file location where data is saved) using the Data File Settings menu, under Logs.
Convert the raw obs to RINEX, using RTKLIB tools or a similar tool.
The data saved by SNIP is in the same format that the data arrives on. Hence if your data stream is in RTCM3, that is what the raw data file will be in. Many tools can convert from RTCM3 (or from the GNSS proprietary data format) to RINEX which is used when processing your observations. Most GNSS vendors will provide you with a tool to do this, otherwise the free RTKLIB tools are very popular.
Then zip it (this is not required but saves time transferring the file)
Submit the Data
Submit the data set to CORS OPUS, here is an article with further details.
(OPUS requires a data set with both L1 and L2 data for its ionospheric models)
OPUS requires only your email address, which is used to return the results to you.
or Submit the data set to the Canada NR PPP service.
(This service operates on L1/L2 data but it is unique in that it can also use L1 only data sets)
You will need to set up a user account, which takes <5 minutes)
The data submission site is below.
They also have a handy standalone application you may wish to download and use if you do this often.
Use the Data
The data set you get back will contain the estimated position expressed in the different coordinate systems. Enter it into your system.
Hint: When the ECEF coordinate system is used you often have the go back and forth from LLH. Here is a simple page with links on how to convert EFEC to LLH and back so you can enter it into various tools including SNIP.