There are several ways data can be entered. If you know all data, you can enter it manually. However, if the ion is precent in the PubChem database (<https://pubchem.ncbi.nlm.nih.gov/>) the easiest way is to go to the subsection "pure substance" which is marked as blue in the figure.
You then get a new set of data fields to the right. This section is connected to the PubChem database. If you provide one of the following: smile, cas-number, inchi, inki-key, or pub-chem ID, you can press the save icon (upper right corner) and the rest of the data should be populated automatically. Please check that data for the right ion has been fetched before you move on to the next stage.