Target matches 100% of the first 5% you contribute to your 401k. So, dollar for dollar, up to 5% of your pay. You can contribute more if you want (I do). If you are grandfathered in for the pension like I am, you still get quarterly contributions from Target into your pension account. To be eligible for the pension, you had to have originally been hired by Target before December 31st 2008.
To answer the OP's question, yes, you can rollover your old 401k into your Target 401k. However they will not do any matching contributions on rollovers. The matching only happens when you contribute from your actual Target pay. It's not a bad idea to rollover your old 401k into Target's 401k, as Target has a surprisingly good fund selection. You are going to have to get access to the Target Pay and Benefits website, as there are forms you need to download/print from the site that you use to do the rollover.
Basically what happens is you tell whoever manages your old 401k that you want to do a rollover into your new employer's 401k. Your old employer will either send you a check for the full amount, which you immediately send to Target benefits with those forms you downloaded/printed, or they send it directly to Target. It depends on your old 401k and who manages it.