1- Open Affinity Designer.
2- Create you shape/design and select it. Click on the colour picker tool and fill with colour.
3- To make a gradient fill, select the gradient fill tool in the left toolbar.
4- Click on your design and drag a line across your design. This will create you gradient.
5- To change the colour of the gradient that you have created, click on one of the gradient points(1) then click on the colour in the colour picker (2).
6- To move the gradient area there are little lines on the gradient you can slide them to adjust where the gradient starts and ends.
7- On the gradient fill line, you can add more gradient colour simply by clicking on the line and adding more points. You can then change the colour to suit your needs.
8- To adjust the angle of the gradient you can click and drag the gradient line to move it on the angle you would like.
9- In the colour picker tool you can select the opacity and make the gradient transparent to suit your needs.
10- You can also adjust the noise by clicking on the opacity icon which will switch it to the noise option. you can then use the slider to adjust the noise.
11- you can also create gradient in the stroke option. to get your stroke colour up click on stroke in the colour picker tool then adjust the width.
12- In the top toolbar select content and in the dropdown box select stroke.
13- Select the gradient tool and click and drag your gradient over your design. this will create a gradient in your stroke. all the above techniques can be applied to the stroke as you did the fill gradient.
14- Another choice you have in the top toolbar is the type of gradient you can create. in the drop down box you have several including the linear and elliptical gradient.