Before creating a chart, make sure that your exploration contains metrics and, optionally, dimensions.
Select a chart type
The first thing you should do is select the chart type you will create. It can be either :
A metric : to display a number or a gauge.
A category : could be any chart type except a metric or a gauge
A time series : to display data in a timely manner, such as in a line chart, a bar chart or a table. Time series provide the ability to aggregate data over time (grouping by day, by week, ...) and comparing your data with the past.
Create the chart
Now that you have selected a chart type, add the metrics and dimensions of your exploration to the query builder, and click on run query.
You will see that the query will be converted to a chart in the visualisation panel.
You can also change the visualisation type by clicking on the icons at the top of the visualisation.
Customise the chart
You can customise the chart using the option panel on the right. The available options will vary depending on the visualisation type you have selected (line chart, pie chart, map, ..).
Save the chart
Finally, you can save the chart by clicking on the save button on the exploration page, and add it to a report or save it as a question.