This is a huge subject and one that simply cannot be answered in one single little blog article, but you can be sure that if you keep comming back to the computer fixer blog you will find good sound advice as to what to do.
You should make sure that any antivirus software you have is not going to run out of its updates without you renewing it first. All the common antivirus products will allow you to see when this is going to happen. Make sure that you renew your licence at least a week before it runs out and more like 10days before if there is a bank holiday comming up.

Fully update your browser and your antivirus software and your operating system, that is three things, lets count them, one, two, three.... "never ever be unprotected" especially when it comes to a computer used on the internet.

If you use your computer a lot then update your antivirus software a lot, this could mean forcing your antivirus software to go and get an update at least once a day!!

You must keep an eye on your browser, if any thing pops up to say that your computer is infected with a virus, you must treat that as an actual virus attack, s DO NOT Click on anything at all, instead disconnect from the internet by pulling out the cable connecting you to you router, or drop the wi-fi connection, then initiate a complete scan and whilst that starts up make a note of which web page you were on when that message popped up. make a note not to return to that page or indeed that web site....

Some of the earlier versions of Microsoft Explorer are not as secure as the more recient versions, and added to this you may find that any specific version of IE (Internet Explorer) may have some updates that you would be wise to apply to it..... perhaps you do not no how to do that? Well as always at the Computer fixer blog we tell you how...
IN IE there is a whole bunch of settings you can change......... go and open up the Internet Explorer browser, then go to tools ! Internet options ! then choose The last tab Advanced. Now scroll dow to find a radio button, it is square and

says Automatically check for internet Explorer updates, tick that and then click on apply, then tick ok. Now you are done.