To use your own Singularity image w/ GlideinWMS you can:
- download your full image is possible if the VO allows it but not recommended (a lot to transfer for each job).
- publish the image in the OSG CVMFS (see below)

To publish the image in CVMFS and use it:

Publish the image to Docker hub

Add to the list of OSG images

Here the OSG documentation:

The suggested method is to send an email to OSG with your image string ORGANIZATION/REPOSITORY:TAG

Alternatively, you can fork the repository, add the likes to docker_images.txt, e.g. in a new branch of your repo, and make a pull request against master of the OSG repository with your changes.

Use it from the job

Add to your condor submit file of the job:

+SingularityImage = "full_path_to_the_image" 

Or use a -l option in JobSub:
-l '+SingularityImage="full_path_to_the_image"'

This command allows you to select your image to use to run your job. This is not a requirement to use Singularity, it works only if Singularity is enabled, otherwise, it will be ignored.
I.e. your VO and the Resource negotiated to use Singularity, e.g. by setting GLIDEIN_Singularity_Use = PREFERRED or REQUIRED