The key thing is to set the type to "radial". You can use the GRD presets as is but you can also combine them in millions of ways using blending modes as well as opacity. The blending mode for the gradient tool is set via the top bar / options in PS. You can add them with the same set of stops / color as well as different sets of stops / colors as well as adding them using different blending modes such as lighten and difference (my favourite) so you can select any number of the presets included in the current panel as well as adding any of the additional sets. You can also also combine them in different image modes as well such as 16bit or 32bit. You can also add the radial presets to a layer and create multiple layers and the advantage of that approach is that you can remove the items at any point as well as perhaps use the layers with layer comps and then you can change the position as well as opacity etc to create even more effects. You can also then combine the effect with the video timeline in PS to create surreal ripple effects over a timeline and then rendered as a MP4 video.
If you want to create an interesting Psychedelic ripple and want the Photoshop gradient to be all located from the center then setup up a guide using the view menu and new guide layout. You can then center any radial colors from that center or from another position (the same, for consistency)
You can then apply them over and over from one particular center point and using a difference blending mode, you can generate a seriously complex circular / contour artwork. You don't have to use them in the same blending mode and you don't have to use blending modes, you can use them with opacity as well or perhaps use presets which include transparency to create even weirder ring artworks. You can also combine the rings with other effects as well as ripple to create awesome psychedelic effects from the 60s - great for t-shirts etc.
You can find the ripple effect / filter via the filter (distort menu). Set the size to large and set the amount to 999% - perfect for creating an interesting 60s themed effect. You can also then manipulate it even further if you add image adjustments. You can also use the presets (before the ripple is applied) and then turn the entire artwork into a smart object via the layer menu smart object command. You can then use the smart object with a smart filter ripple which enables the effect to be changed from extreme / large to subtle. You can also add multiple ripples as well as multiple other effects and with the latest versions of CC, you can now add additional smart adjustments that can be used to totally change the color of the effect such adding additional 60s vibrancy as well as perhaps turning the image into a black and white or sepia effect via hue / saturation adjustment. You can also create even more odd color combinations and ripples by using blur filter effects and posterization (as well as oil paint filters) or use the blur and cutout (from the filter gallery / gallery effects plugins). Such a pity that the posterization tool doesn't split the colors into layers
You may find the Photoshop gradients of interest and use. You can use any of the 32,000 presets included in the set to create all kinds of colorful ripples especially combining them using blending modes
Tutorial on the subject [Youtube] The above video shows the effect created and described. Of course, you can use any number of different combinations than the ones used in the video.
Instead of using a distort filter, you can use a tool such as liquify (filters) and create the ripple manually by dragging the pixels out from the center of the image using a low setting for the liquify brush. You can then combine the results with blurs / posterizations etc. One useful feature of the liquify is that you can click the 'show guides' feature and see the guides created to show the center for the liquify and the ripple