Once you know:
the structure that you will be using in your writing
and how to identify the 'quantity expression' (or QA) of the graph or chart
then you're ready to practice writing your introduction. Once you get into the habit of this it becomes quite easy to do. There is a formula you can use, which is:
The graph shows + QE + [where] + [when].
You want to be able to use synonyms for 'the graph' (e.g. bar graph, line graph, pie graphs, chart) and also for 'shows' (e.g. depicts, illustrates, reveals). So for example:
The line graph depicts the number of electronic items (desktops, laptops and tablets) sold over a six month period, from January to June.
That's it. In the example above, we are not told 'where' the graph relates to so we can not include that information in our introduction. Let's look at another example:
The pie graphs illustrate the contribution of eight sectors to the Turkish economy in 2000 and 2016.
The more you practice writing introductions, the more comfortable and confident you will become. You will also become quicker, which is important in the IELTS writing exam. A couple of things to remember:
Always use a synonym for 'show'
Always use the present simple tense for 'show', 'depict', 'illustrate' etc
Always include the time (e.g. year) at the end of your sentence