The TCGA methylation data is available as open access Beta (β) values from the Illumina Infinium 27K and 450K Human Methylation arrays. You can download all of this data from the GDC Legacy Archive. Here, I have configured a listing for ovarian cancer (TCGA-OV):
To download the data, download the sample manifest for each listing and then use the GDC Data Transfer Tool. Once you get all of the data, you can then begin to think about a strategy of aligning them in order to find mutations overlapping methylated regions.