Some friends wanted me to teach them how I make and use watermarks for my photos, so here it is! I hope it's useful :)
To make your watermark:
Go to the Picmonkey website. Open 'collage'. You'll have to choose a photo so the editor will open, but you won't be using it. Don't worry about it.
The collage editor will open with a three picture collage template. Close two of the boxes by clicking on the 'x' in the top right corner. You'll be left with one big (empty) picture box.
Now you need to make it transparent. This is the whole trick behind making a watermark - eliminating the background by making it transparent. In the menu to the left of the screen, click on the painter's palette (bottommost icon) and select 'transparent background'. The picture box will have become a dotted outline, with no fill.
Select 'edit' from the toolbar at the top of the screen. It will give you a pop-up box; click 'open in editor'. Now you're in the main editor and your picture box will have a checkerboard effect in it. This indicates that the background is transparent, just like we want it to be.
Choose the type option from the menu on the left-hand side of the screen (the 'Tt' icon). Choose your font and click the 'add text' button above the font list. A text box will appear on the screen. Write whatever you want to in it, eg. your business name or website url. I like to centre my text. Click outside the text box to de-select it. Now go to one end of the text box and hover the cursor over it to get the stretch function (a horizontal line with an arrow at each end). Use this to drag the box outwards, making it longer than the picture box. Do it at both ends if you need to. This is so that you can make the writing bigger without it making itself into two lines.)
Select your text and, using the text editing box, increase your text size until it almost touches the sides of the picture box. Later on, when you go to use your text as a watermark, you'll be able to adjust the size to suit your needs, but saving it this big means that the resolution will be higher in the finished product.
At this point you choose what colour and opacity you want your watermark to be. I have two versions: one in plain old black and one in white with a 25% fade. Adjust these by selecting your text and using the tools in the text editor.
Next, select the 'crop' tool from the left-hand menu. It's the top one, shaped kinda like a square. A highlighted box will appear on your screen. Use the circles at the corners to drag and manipulate the box until it surrounds your text, but only just. You want to crop very close to your text. Click 'apply'.
Head to 'save as' in the top toolbar, and save your work.
To use your watermark:
Exit this screen. Choose 'edit' on the Picmonkey homepage. Open a photo. Select 'overlay' (the butterfly logo) from the left-hand menu. Choose 'your own' at the top of the list, and upload your watermark from wherever you saved it to. It will appear on the photo, in a box of it's own. You can drag the corners of the box to adjust the size of your watermark, and can click in the centre of the box to reposition it on the screen. The antenna-like circle at the top of the box can be used to rotate it.
When you're happy, save your work as before. Done!