Hi GallucciArt,
Welcome to Affinity Forums
If it's a simple object filled with a gradient (no Layer Effects etc), select it then go to menu Edit ▸ Copy, select the other object then Edit ▸ Paste Style.
If you want/prefer you can also save the gradient to the Swatches palette for later reuse. To do it select the object with the gradient then go to the Swatches panel -create a new Document Palette if necessary clicking the menu icon on the top right of the Swatches panel and selecting Add Document Palette - then click the small palette icon on the right of the category dropdown to add that gradient as a fill to the document palette you just created. To apply it to another object, select that object and click the fill you just created in the Swatches panel.
GallucciArt got a reaction from John Rostron in colors change