Stop Spam Email

I’m sick of turning on my PC in a morning and finding emails headed up with things like “sister ra’ped in toilet”. It’s sick and offensive and I don’t know how stop it. I’ve done the whole “this is spam” and “block sender” bit in my email settings but I’m still getting loads. How did they even get my email addresses????
Sorry for being thick but where’s the spam filter and how do I turn it on?? I use Microsoft Office Express 6.

I keep getting emails that contain random long messages of a similar layout, but the sent from address, is different everytime. This means i can’t put the address in the spam filter because it is different each time. It’s more of an annoyance than anything. Please help.

I get tons of spam in my yahoo email account. How do I stop it?
The spam filter is turned on.

My SPAM Filter recently started letting more SPAM in, I cannot get it to reset and am having to dump lots of SPAM.