All the infoboxes can be found here.

Copy the code displayed on the left and just paste it into the source of your page (do not use the visual editor but the classic rich text editor). The code on the left is the clean/simple version of the infobox where you just have to add in your information after the equal sign. All the overwhelming and complicated HTML sorted for you. 

You will need to edit it in Source and not visual as the infobox will not be displayed in visual mode. Ignore the |hideb= you see (unless you want to hide the column it stands for. In that case, add a letter after the =, this will hide the section of the infobox it stands for) and just add information in the other fields. Once you start doing that the information will present itself on your page but you can only see it by either clicking Preview:Mobile/Desktop or after publishing your changes which will automatically take you out of editing mode and show you your page.

To add bullet points press enter in the desired field and add * to make bullet points pushed further to the right use two ** like so: 

Bullet point example

When adding your image to the infobox please remove the "|thumb" and make sure the size is "263px", this way the image is perfectly centred in the infobox.

To make a signature you could use this website . I usually use it, just make sure (my recommendation) the background is black so it blends in with the page.

If you have any questions just drop a comment below ;)