OK, that's a pretty comprehensive plasmid map, most are simpler. From it I can see that you actually have two tags on your protein - HA and Glutathione S transferase (GST), these are both N-terminal (i.e. appear before the start of your gene of interest), and that the HA is before the GST. The MCS in this case has been split into at least two parts - there will be a parent plasmid with it as one contiguous region, but yours starts with BbsI (position 1688 from the ori), and ends with BamHI (3996), the insert is between these two positions and is the reason the MCS is split. The HA and GST were already in these plasmids as you can see from the cloning information, which states that the insert was cloned using SalI and NotI.
I can also see, by comparing the restriction sites between this vector and pcDNA3.1(+), that you have some that are compatible, but these are in a different order in the two plasmids. This would result in your insert going in backwards, so you can't do a common subcloning into that vector. So, your best option is to amplify the insert using PCR and add the desired restriction sites and make it easy for yourself.
The HA can be either on the plasmid when you clone in, or it can be part of the insert. If you want your gene as it is with both tags, simply get the sequence from Addgene, look for the open-reading frame (ORF) that encodes your gene of interest and design primers based on that. The gene specific sequence will be the first and last 20ish bp of your insert. Take a look at the plasmid you want to clone into - look at the MCS and choose two restriction sites. I recommend sticking with two of the more easy ones, something like EcoRI and BamHI works well for pcDNA3.1. If you are using pcDNA3.1 and those sites; EcoRI will go on the forward primer and BamHI on the reverse so that the insert will be oriented correctly when you come to express it. Now you simply do a PCR, digest insert and target, then ligate. Note that EcoRI and BamHI work well in Phusion PCR buffer, though the HF versions do not. See here for more information on the enzymes and their activity in PCR buffer.
If you do not want the GST tag (I wouldn't, tags can interfere with folding of the proteins...). You can add the HA tag (see here for sequence) to either the forward or reverse primers, depending on whether you want a N- or C-terminal tag. Note that if you want it N-terminal, you need to add an ATG start site before the tag sequence, so the primer would look like this:
NNNNNN GGATCC NNNNNN ATG TACCCATACGATGTTCCAGATTACGCT NNNNNN YOUR_DNA_SEQUENCE
6bp BamH1 spacer start HA tag spacer your_DNA...
Spacer after tag must be multiples of 3 to keep sequence in-frame. Conversely if you wanted a c-terminal tag you would need to add a stop codon. The annealing temperature of the primers does not include the non-sequence specific stuff like the tag, just work it out off your DNA sequence.
There's a lot more to it than that - go to your local university library and find the book "Molecular cloning: a laboratory manual" by Sambrook et al., there is a lot of excellent information in there.