The Affinity Photo cloud tool can be found in the tools panel along with the other vector tools. If it is not there, you may need to go to the customization command in the view menu and update your panel.
It is used to create a shape layer. You can add it to any size, rotate, shear etc and also you can modify interactively via the control handle to change the radius. The same setting can be controlled also via the top bar along with the number of bubbles generated by the tool, by default the number of bubbles is 12. You can set the bubbles to well over 100 and more to create truly intense designs randing from bubbled designs to star burst designs and more.
The shapes can be duplicated and re-sized and combined in multiple ways and you can also use the layer menu and geometry to subtract the front shape etc. You can create the shape layer design multiple times in many different sizes and angles and bubbles and radius settings. If you have more than one of the shapes selected and you are using it then you can also the sliders and the values will be updated for all the selected shapes.
You can add effects to the shapes via the filter menu as well as the layer menu and live filter layers but in both cases the design will be converted to pixels and will no longer be a vector shape.
You can also use the designs with features such as the pattern from selection found in the layer menu. You will have to convert the design to a pixel via the layer menu and rasterized before you can use the pattern feature. Once it is a pattern layer, works even better if you go to the top left and select the mirror option to generate a seamless tile design.
You can set the fill for the shape to a solid color or a swatch as well as a gradients and also to a bitmap pattern via the control bar. You can also add a stroke as well as a dashed stroke as well as a more variable width stroke via the pressure settings.