The answer to your question depends upon whether you just mean in your web browser or in general (e.g. on your desktop).
As has already been indicated, pressing Ctrl and + together enlarges the text size in all major web browsers. (Pressing Ctrl and - makes it smaller. Pressing Ctrl and 0 returns it to the default size).
To make text easier to read in general, go the the 'Ease of Access Center'. The way to get there might vary across different versions of Windows but, hopefully, using the Search box will work in all of them:
Click the Start button
Start to type 'ease of access' into the search box.
You should then see 'Ease of Access Center' in the search results above the box. Click on it.
Then click on 'Make the computer easier to see', followed by 'Change the size of text and icons'
Select your preferred size and click on 'Apply'
[NB: Those instructions are based upon Windows 7. It might be a little different in Windows 8 or 10 but you should still be able to get there].