Now you have filled in every PICO element / building block (Step 2 and 3) you can combine the different elements / building blocks for the end result.
To be able to combine your search terms and search actions you need boolean operators. You can use:
AND = articles with all search terms
OR = articles with one or another or all search terms
Pubmed remembers all your search actions. Via 'Advanced' you will find your search history.