A person who has the common cold will be infectious to others a few days before the cold symptoms start occurring and for the entire duration of the cold and until the cold and cold virus is gone.
When the cold is fully gone then you're no longer infectious to others which can be for 1 to 2 weeks.
You should avoid going back to work or school for at least 24 hours after the cold goes away so as not to infect others.
A few things you can do to help with the cold is to eat healthy, stay hydrated get plenty of rest and keep some moisture going in your room or home to keep the air from drying out.
And in 1 to 2 weeks you should be feeling better and the cold should go away.