Knitting letters?

I’m not new to knitting…but I’ve done very little in the way of anything…well, different than just a normal stitch. What I’d like to do is make some like, block squares with letters on them.

I have never knit with two different colors before…I have never done any kind of pattern with two colors or anything.

What I’d like to do, is make a blanket out of knit squares…and in some of the squares I want to knit letters spelling out our family name and stuff like that…I just have no clue how to make letters inside what I’m already knitting…with another color…am I making sense?

I feel kinda silly…'cause I’ve been knitting for 10 years, yet know so little…but I would really like some help with this if you could…thanks in advance!