Selenium is not exactly the most well known piece of software and infact is actually quite difficult for a lot of people to use. This is because it is a web development plugin and obviously you will need to be a web designer, web developer or equivalent in order to be able to understand it and actually find a use for it. Selenium is primarily used to find any potential bugs or issues with the coding of a site, app or any other kind of web development and is used to create a virtual environment in which you can test it and find and iron out these problems.
Learning Selenium initially is probably the trickiest part about using it. Where a lot of people will say that they pick up on how to use newer pieces of software very quickly you may be mistake or surprised by how difficult it can be to learn Selenium. It is easy enough to learn how to use different word document programs such as WordPad and Microsoft Word because you will have used them before in the past, but these are all similar and therefore easy to transition to. If you were trying to learn to use something that you never had done before (e.g. video editing software after never making a video before) you are going to be stuck with a very difficult time ahead of you. No matter how much you say you have learnt of something in a short space of time you are very unlikely to know the ins and outs of it and how to use the software as efficiently as possible (for instance adding custom effects and sounds to videos rather than just putting in raw footage and text). Selenium requires more than just a trial and error or guide-based strategy, and so there are a couple of ways in which you can learn to use it properly for a relatively low cost and a very short amount of time.
The first way in which I would suggest that you try to learn to use Selenium would be through the help of an online class, which can be found at numerous websites including www.edgewordstraining.co.uk who offer online Selenium courses that last around 3 days and will have you completely clued in on everything to do with the plugin. Saving what could be weeks on trial and error efforts to learn Selenium in order to get back to your designing and bug fixing so that you can work more efficiently than ever is very simple to do and will increase your work rate exponentially, which is a great trade-off for simply taking a short course and missing out on a couple of days.
You can also find classroom based courses at Edgewords, and they have a location in London where you can do this. The classroom is more suited to some people, and so in order to find the most efficient way for you to learn to use Selenium make a decision on whether a classroom or online environment is best for you.